Pseudocycas insignis Nathorst.
The fronds of this Cenomanian species from the West of Greenland reach a breadth of 16 cm.; the rachis, 1 cm. broad, has two parallel ridges on the upper surface and to these are attached at a wide angle the broad bases of narrow linear pinnae reaching a length of 9 cm. and a breadth of 2–3 mm. (fig. 617). The pinnae are thick and separate and each has a double ‘midrib’ consisting of two parallel lines (fig. 617, B) which are occasionally replaced by one. The so-called double ‘midrib’ represents the two prominent ridges bordering the groove. The stomata, confined to the median groove, are approximately circular and the short epidermal cells have sinuous walls[1648].
Pseudocycas Steenstrupi (Heer).
Nathorst refers this species, described by Heer as Cycadites, from the Cenomanian of Greenland, to Pseudocycas on the ground that the epidermal cells are like those of P. Steenstrupi and the stomata are confined to a median groove. Heer figures an impression in close association with the frond of this species which he identifies, without any adequate reason, as a carpellary leaf like that of a Cycas.
Pseudocycas Saportae (Seward).
It has recently been shown by Miss Holden that this Wealden English species[1649] has the epidermal characters of Pseudocycas. In external form it agrees closely with Cycadites tenuisectus Sap.[1650] from Lower Cretaceous rocks in Portugal, but nothing is known of the epidermal features of the latter type. The rachis is broad and flattened and bears alternate or sub-opposite pinnae of uniform breadth attached at right-angles or obliquely to its upper surface (fig. 618). The pinnae are 6–7 cm. long and about 1 mm. broad; their bases are slightly expanded and the apices sharply pointed. Miss Holden[1651] finds that the median rib is sometimes double and that the middle region of the lamina is covered with stomata; the epidermal cells have sinuous walls and stomata occasionally occur on each side of the main median stomatal area. Dr. Halle[1652] of Stockholm, who has examined cuticular preparations made from English specimens, confirms Miss Holden’s observations as regards the stomata, but he shows that there is no evidence of the existence of a midrib in the strict sense, the appearance of a single or double median vein being due to the presence of a dorsal stomatiferous groove, the edges of which would produce an impression on the matrix of a double vein or, if the groove became narrower, the impression would suggest a single midrib.
Pseudocycas Roemeri (Schenk).
This Wealden species recorded from North Germany[1653] and the Sussex coast[1654] has broader pinnae laterally attached to the rachis. Miss Holden describes the stomata as covering the whole lower surface of the pinnae except over the midrib. This description must be revised in the light of Halle’s results obtained from an examination of the cuticle of the type-specimen of the species in the Berlin Museum. He finds that the edges of the pinnae are strongly revolute and thus form a deep dorsal canal which is almost closed[1655], a form of lamina, as seen in section, very similar to that of an Empetrum leaf. The stomata are confined to the groove. It may be that the specimen examined by Miss Holden is specifically distinct or, as Halle also suggests, the cuticle obtained from the English fossil may not represent the whole surface but only the walls of the canal with possibly a portion of the cuticle of the outer dorsal surface. This type of leaf described by Halle is similar to that of P. insignis with the xerophilous character intensified.
Cycadites Saladini Zeiller.
This species was founded by Zeiller[1656] on fronds from the Rhaetic of Tonkin reaching a length of 40 cm. and 2–8·5 cm. broad with a rachis 3–4 mm. wide bearing contiguous linear pinnae 1·5–4·5 cm. long and 1·5–3 mm. broad with a more or less contracted base and a rounded or obtusely pointed apex. The pinnae are attached almost at right-angles or at an angle of 60°–80°. There is a clearly defined midrib.
It is not improbable that were the structure of the epidermal cells known this species would be found to be another example of Pseudocycas.
Cycadites rectangularis Brauns.
This species[1657], first recorded from Rhaetic strata in Germany, differs in the narrower and more acutely pointed pinnae from C. Saladini. Miss Holden describes the midrib as double, but until specimens are found which admit of an examination of the cuticles it is impossible to decide whether it should be transferred to Pseudocycas. The species is widely distributed in Rhaetic and Jurassic strata and specimens are recorded from the Lias of Lyme Regis on the south coast of England.
Cycadites Renaulti Lignier.
This species, from the Middle Lias of Normandy[1658], is founded on fronds 2·2–2·6 cm. broad with a rachis 3 mm. in breadth bearing laterally-inserted pinnae almost at right-angles 11–12 mm. long and 1·25–1·50 mm. broad; it is very similar to C. rectangularis which occurs in the same beds.
II. Nilssoniales.
NILSSONIA. Brongniart.
This genus[1659] was named after the Swedish naturalist Nilsson who had figured certain plants from the Lias of Höör referred by Fries to the Ferns: these were named by Brongniart Nilssonia brevis and N. elongata and classed with the Cycads. The type-specimens of the latter species are regarded by Nathorst as a form of N. brevis. The history of the genus is fully discussed in Nathorst’s able monograph[1660]. Nilssonia, founded on fronds which with one exception are known only as casts or impressions, may be thus defined: Fronds with circinate vernation, at least in the type-species Nilssonia brevis (fig. 619, C, D), similar in shape to the leaves of Scolopendrium vulgare and Polypodium irioides and to such unusual forms of Cycas fronds as those reproduced in figs. 384, 387, I[1661], in which the laminae of the pinnae are concrescent and form a continuous or deeply cut lamina. They may reach a length of 60 cm. and a breadth of 10 cm. and some specimens are known in which the leaf is less than 1 cm. in width. The lamina is occasionally entire, but in the great majority of cases it is more or less deeply cut into segments of unequal breadth varying considerably in size and shape even in the same species, usually deep and truncate and sometimes long and narrow (e.g. N. pterophylloides, fig. 619, B). An important distinguishing feature is the attachment of the lamina to the upper face of the rachis which it covers: the extension of the lamina over the surface of the frond axis and the rare occurrence of branching of the veins are characters in which Nilssonia differs from Taeniopteris. The veins are given off at right-angles or obliquely from a very narrow groove occupying the median line of the rachis; they are nearly always simple and in some of the more fleshy leaves, e.g. N. brevis, they are seldom visible. The surface of the lamina may be smooth or transversely corrugated. The rachis forms a prominent rib on the under surface of the frond (fig. 620, A) and may be continued beyond the lamina as a short petiole. Epidermal cells polygonal or rectangular, with straight walls in contrast to the sinuous walls of Taeniopteris; some of the cells bear strongly cuticularised papillae, possibly the bases of hairs (compare the hairs on the fronds of Acrostichum crinitum, a Fern with leaves similar in shape to some of the large entire fronds of N. orientalis though relatively broader and with anastomosing veins). Stomata usually confined to the lower epidermis and not very numerous; guard-cells of rounded contour and without any special thickening surrounded by 6–8 accessory cells with thickened walls (fig. 611, B) forming a chimney slightly raised over the stomatal pore[1662]. In Nilssonia the guard-cells do not exhibit that regularity of orientation which characterises the stomata of Ptilophyllum, Otozamites, and other Bennettitalean fronds. Little is known of the anatomy of the leaves: in a petrified leaf of N. orientalis[1663] from Upper Cretaceous rocks in Japan there is no palisade-tissue and small groups of sclerenchyma occur above and below the veins. The xylem appears to be centripetal, but the preservation is far from satisfactory. A few secretory canals were found near the edge of the leaf. We have no certain knowledge of the reproductive organs. The small circular projections figured by Schenk[1664] on some leaves of Nilssonia polymorpha as sporangia have no claim to be so regarded. In the description of N. brevis reference is made to some seeds discovered by Nathorst which may belong to that species. Nathorst suggests the possibility that the Rhaetic fossil Stenorrachis scanicus Nath. may be the seed-bearing shoot of a Nilssonia, either N. brevis or N. polymorpha, and if this surmise is correct it almost necessarily involves the genus Beania[1665] which has been tentatively referred to the Ginkgoales though without any convincing evidence to support such connexion. Nothing is known of the stems: the occasional occurrence of leaves converging towards a common support points to a Cycadean habit. It is possible, as Nathorst suggests, that the Rhaetic species Bucklandia Saportana[1666] may be the stem of a Nilssonia.
Nilssonia is especially characteristic of Jurassic and Rhaetic floras; it occurs also in Triassic beds and extends into Cretaceous floras.
Nathorst instituted the genus Nilssoniopteris[1667] for some specimens from the Yorkshire coast which he believed to be examples of Nilssonia tenuinervis on the ground that the veins are dichotomously branched and the epidermal cells have sinuous walls. Mr Hamshaw Thomas[1668] has, however, shown by an examination of the specimens in the Stockholm Museum that they belong to Taeniopteris vittata, and Prof. Nathorst agrees with this conclusion. The name Nilssoniopteris must therefore be abandoned. Miquel[1669] proposed the name Hisingera for some Nilssonia fronds, but it has not been adopted.
Nilssonia polymorpha Schenk.
Linear fronds varying considerably in breadth and in the degree of dissection of the lamina, which may be entire; the margin may show broad and shallow crenulations or there may be a few narrow and deep sinuses cutting the otherwise entire lamina into long and narrow segments. More usually the lamina is divided to the rachis into numerous truncate segments traversed by parallel, simple, veins extending from a narrow groove in the middle of the rachis on the upper surface of the frond (fig. 619, E). The veins run in very narrow grooves in the generally flat but occasionally corrugated lamina[1670].
This species agrees very closely in habit with N. compta and N. brevis and, as Nathorst points out, it is in some cases almost impossible to distinguish Nilssonia polymorpha from N. brevis. Some of the fronds from the Rhaetic of Franconia described by Schenk as N. polymorpha are examples of N. brevis. In N. polymorpha the distal ends of the segments are blunter, the lamina is much less folded and when folds or corrugations occur they are less regular than in N. brevis. The epidermal cells are polygonal and have thick, straight, walls: oval or circular papillae occur both on the lamina and rachis. The stomata, confined to the lower surface, are between the veins and each is accompanied by a ring of subsidiary cells (cf. fig. 611, B). N. polymorpha is a member of Rhaetic floras and is recorded also from Liassic rocks at Höör[1671].
Nilssonia brevis Brongniart.
This species[1672] (fig. 619, C, D), one of those from Höör on which the genus was founded, has been very fully investigated by Nathorst[1673] whose researches have cleared up many obscure features. The young fronds are circinate like those of Ferns and Cycas. The linear fronds agree generally in habit with those of N. polymorpha and N. compta, but the lamina is thicker and is characterised by regular transverse corrugations; the veins are very rarely visible except in young leaves which have not reached their full thickness. The fronds may be 50 cm. long and vary in breadth from 1·5 to 12 cm.; the petiole is very short or the frond may be sessile. Between the regular grooves on the upper surface the lamina is more or less convex; seen from below the grooves are represented by ridges and between each pair of ridges there are parallel folds, sometimes three (fig. 620, B) or as many as six; and where the segments are narrow, that is the strips of lamina between two grooves (or ridges), there may be only a single fold which gives the appearance of linear segments with a single midrib as in Cycadites, a misleading resemblance of special interest in reference to the Nilssonia fronds described by Oldham and Morris[1674] and by Feistmantel[1675] as Cycadites rajmahalensis. Owing to the fleshy nature of the leaf the difference between the upper and lower side is particularly well marked in this species. The lamina may be more or less entire, but is usually divided by deep sinuses extending to the rachis into truncate or distally tapered segments varying in breadth (fig. 619, C, D), the narrow segments being characterised by a more pointed apex than in N. polymorpha. The structure of the stomata and epidermal cells is of the type described in the definition of the genus. Strongly cuticularised papillae, incorrectly described by Schenk[1676] in N. polymorpha as stomata, occur on some of the epidermal cells: these may be the bases of hairs. In some preparations Nathorst found patches of a resinous substance, an interesting discovery in view of the occurrence of secretory canals in the petrified leaf of Nilssonia orientalis described by Dr Stopes[1677].
Nilssonia brevis occurs in Upper Rhaetic and Lower Liassic strata.
Nilssonia pterophylloides Nathorst.
A Rhaetic Scanian species originally referred by Nathorst[1678] to Nilssonia but later removed by him to Dioonites[1679] and in 1909 reinstated in Nilssonia[1680] on the ground that the lamina covers the upper face of the rachis. The segments are fairly uniform in breadth and linear; they reach 10 cm. in length and are usually 5–7 mm. broad; the lamina is slightly tapered towards the apex (fig. 619, B). There are 3–10 parallel grooves on the upper face of the segments and between each pair is a single unbranched vein. In close association with portions of three fronds of this species Nathorst found several oval bodies, 1 cm. × 7 mm., which he at first regarded as ‘antherangia’ comparable with the sporocarps of the Hydropterideae, but an examination of the carbonised tissue demonstrated that the small rounded bodies contained in each of the ‘antherangia,’ originally believed to be pollen-sacs, are grains of resin internal to a cuticle of thick-walled cells and probably formed by secretory sacs in a fleshy tissue. Internal to the resin-bodies is a second cuticle which may be the remains of a nucellus, the outer cuticle and the resin belonging to the sarcotesta. Nathorst’s careful examination of these fossils shows that they are seeds (fig. 619, A) and were probably borne on plants of N. pterophylloides, though an accidental association is not improbable.
Nilssonia compta (Phillips).
Broadly linear fronds varying considerably in size and in the breadth and number of the truncate segments. In some cases the fronds exceeded 40 cm. in length and had a breadth of 9 cm. (fig. 622). The veins are simple, parallel, and fairly prominent and the lamina shows clearly the attachment to the upper surface of the rachis which is covered by it as in all species of the genus[1681]. The structure of the epidermis and stomata has recently been described by Thomas[1682]. Brongniart mentioned in the Prodrome a species from the Lower Oolite of Yorkshire under the name Pterophyllum Williamsonis[1683], but in a later work this is given as a synonym of N. compta. Nilssonia compta bears a close resemblance in habit to N. polymorpha; it agrees also with the large fronds described from the Upper Gondwana of India as Pterophyllum princeps[1684]. Since attention was first called to this similarity an examination of several of the figured specimens has convinced me that the Indian fronds are either identical with or at least closely allied to the European leaves. The apparent lateral attachment of the lamina in the drawings published by Oldham and Morris and Feistmantel is due to imperfect preservation; the lamina ends in two raised ridges, and the discovery of a specimen in which the lamina completely covers the rachis confirmed the impression made by the other specimens. The Amurland Jurassic species Nilssonia Schmidtii[1685] Heer though probably not identical with N. compta is a very similar type; it was originally described by Heer as Anomozamites Schmidtii and transferred by Nathorst[1686] to Nilssonia: the veins are occasionally forked near the rachis and are rather farther apart (·5 mm.) than in N. compta and the segments are broader and deeper than in the English species. Nilssonia nipponensis Yok.[1687] a Jurassic species recorded from Japan and North America is another similar type.
Nilssonia orientalis Heer.
In this Jurassic and Lower Cretaceous species, founded on material from Jurassic rocks in Siberia[1688], the lamina is generally entire. The fronds exhibit a wide range in size and shape; they may have the form of very narrow linear leaves barely 1 cm. across or may reach a breadth of nearly 10 cm. The leaves from Middle Jurassic British strata named by Nathorst N. tenuinervis[1689] are probably identical with Heer’s type, and N. Johnstrupi[1690] Heer from the Lower Cretaceous of Greenland may also be referred to N. orientalis.
The veins are at right-angles or oblique to the rachis and are very numerous, three or more in a breadth of 1 mm.[1691] A species recently described by Halle[1692] from Graham Land as N. taeniopteroides agrees closely in habit with N. orientalis: in the southern form the frond may have a length of 40–50 cm. and a breadth of 3 cm. The entire lamina of N. taeniopteroides tapers gradually towards the base and is more rapidly narrowed in the distal region; the petiole is at least 6–7 cm. long: the simple or branched veins, 15–20 in 1 cm., are given off from the axis at a wide angle. The more crowded veins in N. orientalis constitute one of the few features in which it differs from Halle’s species, but the fact that the degree of closeness of the veins is inconstant within the same species renders this distinction of doubtful value. Halle compares his species also with N. densinervis (Font.) originally described as Platypterigium densinerve from the Potomac beds[1693] and afterwards transferred by Berry[1694] to Nilssonia and considered by him to be identical with Fontaine’s Platypterigium Rogersianum. An examination of some of Fontaine’s specimens in the Washington Museum led me to refer the fronds to Nilssonia[1695].
It is impossible to speak with confidence as to the absolute specific identity of N. orientalis Heer, N. Johnstrupi Heer, N. taeniopteroides Halle, and some similar forms; but it is clear that the linear fronds of this type characterised by an entire or occasionally pinnatisect lamina were widely distributed in Jurassic and Lower Cretaceous strata and persisted to the Upper Cretaceous series in Japan. This form of frond is recorded from England, Scotland, North America, Greenland, Spitzbergen[1696], Siberia, Russia, Afghanistan[1697], Japan[1698], Graham Land, and elsewhere. Reference has already been made to a petrified specimen of N. orientalis described by Dr Stopes from Japan[1699].
Specimens described by Salfeld[1700] from the Corallian of Germany as Taeniopteris sp. may be N. orientalis; Bartholin’s N. polymorpha from Bornholm, Velenovský’s Lower Cretaceous N. bohemica and Yokoyama’s N. ozvana from Japan are other examples of fronds which may be identical with N. orientalis[1701].
Nilssonia tenuicaulis (Phillips).
This Jurassic species, while agreeing generally in habit with N. compta, is characterised by the narrow and numerous linear segments with a more acuminate apex. The fronds reached a length of more than 20 cm.[1702] Leckenby’s name Pterophyllum medianum[1703] was given to a specimen from the Yorkshire coast and now in the Sedgwick Museum, Cambridge, which, with Pterophyllum angustifolium, is clearly identical with Cycadites tenuicaulis Phillips. The specific name mediana frequently used[1704] for this type should be given up in favour of the older term tenuicaulis. A species of similar habit is described but not figured by Krasser[1705] as N. Sturii from the Lunz beds. N. tenuicaulis is fairly common in the Middle Jurassic beds near Scarborough and is recorded from the Kimmeridgian of Scotland under the name N. mediana (fig. 614, C)[1706].
Nilssonia princeps (Oldham and Morris).
Oldham and Morris speak of Pterophyllum princeps[1707] as one of the commonest plants in the Rajmahal beds in India. The fronds are characterised by their large size and by the very broad oblong and distally truncate pinnae with parallel and occasionally branched veins. In the specimens figured by Oldham and Morris and Feistmantel the pinnae are cut off at their bases (fig. 623), which form ridges parallel to the rachis: this feature is not clearly shown in the published drawings. By breaking some pieces of rock from a slab containing figured specimens other pieces were found in which the laminae of the bases of segments meet in the middle of the upper face of the rachis. The pinnae vary in breadth from 1 cm. to 3·5 cm. and reach a length of 8 cm.; the distal end is truncate, the lower edge being strongly curved: the segments are slightly broadened at the base. The veins are prominent and parallel, from 0·5 to 0·8 mm. apart. The Rajmahal fronds described as Pterophyllum Morrisianum[1708] appear to be indistinguishable from this species.
Nilssonia Schaumburgensis (Dunker).
This species, first described as Pterophyllum Schaumburgense[1709] from the Wealden of Germany, affords a good illustration of a small type of frond closely resembling the much larger species N. compta. Examples from English Wealden rocks seldom exceed 1 cm. in breadth and are often much narrower; the linear lamina is almost entire or divided into short and broad truncate segments of unequal breadth: the veins are parallel and simple. For figures of this species, recorded from different European localities and from Japan, reference should be made to the accounts by Schenk[1710], Nathorst, Yokoyama, Yabe, and Fontaine.
CTENIS. Lindley and Hutton.
The genus Ctenis[1711] was founded on a piece of pinnate frond from the Middle Jurassic rocks of the Yorkshire coast previously figured by Phillips as Cycadites sulcicaulis. Lindley and Hutton regarded the plant as probably Cycadean and proposed to apply the name Ctenis to all leaves having the general characters of Cycadeae, but with ‘the veins connected by forks or transverse bars.’ While many authors have accepted Ctenis as a Cycadean genus, by others[1712] it has been placed among the Ferns, on the ground that some small circular elevations on the lamina of the segments of certain species are believed to be sori or sporangia. Since Ettingshausen[1713] and Schenk[1714] first noticed this feature Raciborski[1715] has figured several examples from Poland and Staub[1716] records similar circular bodies on a Liassic Hungarian species. In no single instance have sporangia been found. Nathorst[1717] proposed the designation Anthrophyopsis (because of the resemblance of the lamina in form and venation to the leaves of the Fern Anthrophyum) for some Rhaetic specimens from Scania, but as they were subsequently found to be segments of a pinnate frond he adopted the name Ctenis. An example in the Manchester Museum[1718] (fig. 624) from Yorkshire, mentioned by Nathorst in an early paper as probably a new species of Anthrophyopsis, afforded good preparations of the cuticle (fig. 625) which revealed the existence of circular elevations on the outer walls of the epidermal cells: these may explain the nature of some at least of the supposed sporangia. The walls of the epidermal cells are straight. The name Ctenis is applied to pinnate fronds which are probably Cycadean though we have no evidence as to the nature of the stem or the reproductive organs. Ctenis fronds are among the largest Cycadean leaves from Mesozoic floras; in Ctenis hungarica Staub the frond is said to have reached a length of 2 met. and in other species the dimensions exceed those of most pinnate leaves. The stout rachis bears linear or broad-oblong pinnae attached at a wide angle and varying considerably in size and shape; the pinnae are attached by the whole base which is usually broadened and decurrent but in a few cases slightly contracted (e.g. C. Zeyschneri Rac.[1719]). For some fronds bearing broad and basally narrowed segments Raciborski proposed the name Ctenidiopsis in distinction from Euctenis which he applies to the typical forms. The pinnae may be long and narrow reaching a length of over 12 cm., or short and broad: in some cases the frond would be more correctly described as deeply pinnatisect; the apex of the segments is acute, bluntly rounded or truncate. Several veins pass into the base of each pinna and pursue a course approximately parallel to the edge of the lamina; a characteristic feature is the occasional occurrence of oblique cross-connexions between the veins. It is possible that in some species the pinnae had spinous margins as in the pinnae of uncertain affinity figured by Fontaine[1720] as Encephalartopsis nervosa from the Potomac series. Our knowledge of the epidermal cells is very meagre: in the specimen represented in fig. 625 the epidermal cells have straight walls and a central papilla. The genus extends from Triassic to Upper Jurassic rocks.
Ctenis lunzensis Stur.
This species, first recorded by Stur from the Lunz Upper Triassic flora, has recently been examined by Krasser[1721] and compared with the Jurassic species Ctenis sulcicaulis (Phill.) (= C. falcata Lind. and Hutt.) and C. Potocki Rac. No figures or detailed descriptions have been published.
Ctenis fallax Nathorst.
This Scanian Rhaetic type[1722], including Anthrophyopsis crassinervis, A. Nilssoni, and probably A. obovata Nath., is characterised by very large obtusely pointed pinnae reaching at least 20 cm. in length and over 3 cm. in breadth. The veins are often 2 mm. apart and form long polygonal meshes. Nathorst figures small circular patches on the surface of the lamina. Raciborski[1723], on slender evidence, refers a fragment from the Jurassic of Cracow to this species.
Ctenis hungarica Staub.
A species[1724] characterised by very large fronds reaching 2 met., bearing broad linear pinnae almost at right-angles and attached to the rachis by decurrent bases, attaining a length of 21 cm. and a breadth at the base of the lamina of 3·5 cm. and 4 cm. a short distance from the acute apex. The veins are parallel to the edge of the lamina, but Staub does not appear to have seen distinct anastomoses. It is not improbable that Staub’s species may be identical with C. asplenioides (Ett.) from the Lias of Hungary, specimens of which are preserved in the École des Mines, Paris.
Ctenis asplenioides (Ettingshausen).
This species was first described by Ettingshausen[1725] from Liassic strata in Austria as Taeniopteris asplenioides and compared by him to large simple fronds of Asplenium nidus but distinguished by a deeply dissected lamina. Schenk[1726] found that the veins anastomose and adopted the name Ctenis. In habit very similar to C. sulcicaulis, but the pinnae are much broader, exceeding 4 cm., and the veins are 3–5 mm. apart. Only the basal part of the segments is figured by Ettingshausen. Specimens in the École des Mines, Paris, from Hungary have pinnae nearly 40 cm. long and 2·5 cm. in breadth, the parallel veins being connected by a few oblique branches. Both Ettingshausen and Schenk speak of small circular sori on the lower epidermis, though these are not figured nor were any sporangia obtained. This species and other examples of large Ctenis fronds are described by Raciborski from Lower Jurassic rocks in Poland. He figures part of a leaf of C. Zeyschneri[1727] 40 cm. long bearing alternate pinnae approximately 10 cm. long and nearly 4 cm. broad, characterised by obtuse apices, a decurrent lamina, and anastomosing veins closer together (16–24 per 1 cm.) than those of C. asplenioides. In one Polish specimen, C. remotinervis[1728], with pinnae 5 cm. broad the lamina is represented in the upper part of the frond as continuous over the face of the rachis, and—if the drawing is accurate—the frond in this respect differs from typical examples of Ctenis and agrees with Nilssonia. A species of Ctenis with broad pinnae is described by Yokoyama[1729] from the Jurassic of China as C. Kaneharai.
Ctenis sulcicaulis (Phillips).
This type[1730] is more familiar under the name Ctenis falcata given to it by Lindley[1731], but if we follow Lester Ward[1732] in strict observance of the rule of priority, a course from which I have frequently deviated on the ground of long usage, the less familiar designation must be adopted. Fronds pinnate; long and tapered linear pinnae sometimes exceeding 12 cm. in length and 1 cm. in breadth attached obliquely or almost at right-angles to a fairly broad rachis (fig. 626). The lamina is broadest at the base and the lower margin is strongly decurrent, tapering distally to an acute apex. The parallel and frequently anastomosing veins diverge slightly in the basal region of the pinnae. Though usually separate to the base, the laminae of adjacent pinnae may be continuous as in a pinnatisect leaf[1733]. This species is recorded also from North America, and fronds of similar habit are figured by Fontaine[1734] from the Jurassic of Oregon as Ctenis orovillensis: a fragment recorded from Jurassic rocks in Afghanistan as Ctenis sp. may belong to C. sulcicaulis[1735].
Ctenis latifolia (Brongniart).
This species[1736], originally referred to Taeniopteris, was transferred to Ctenis as the result of the discovery of anastomosing veins in the type-specimen in the Oxford Museum. The segments are shorter and broader than in C. sulcicaulis and very similar to those of C. orovillensis Font.