- Fig. 1, Transverse section of shell of Chelonobia testudinaria.
- B A B, Compound rostrum: A being the true rostrum.
- B B, the rostro-lateral compartments, which normally, in the Balaninæ, are quite confounded
with the true rostrum: the sutures separating these three compartments are not continued through the
outer lamina.
- C, left-hand lateral compartment.
- D, left-hand carino-lateral compartment.
- E, carina.
- S S, Sutures, six in number, separating the six compartments.
- a, outer lamina of wall of compartment, whence the radiating, longitudinal septa (left unshaded)
arise, and at the opposite end blend into the indistinct inner lamina, viz. b, (see
fig. 4, in last plate.)
- c′, sheath.
- d, ala, forming, as usual, part of the sheath.
- e, inner portion of the radius.
- f, f, outer lamina of the radius (see b, in fig. 5, in last plate), of great
thickness, and externally deeply pitted;—the sharp ridges between the pits, produce in the
section the points, such as that marked by the outer f.
- 2, Coronula balænaris, shell seen from above.
- 2 a,””section of one of the transverse circumferential loops, formed by the folded wall of a compartment. The wall itself is formed of an outer and inner lamina, with longitudinal septa. The internal surfaces of the loop-part are connected by special shelly plates or longitudinal septa.
- 2 b,””scutum and tergum united together by the opercular membrane (with horny ridges), seen from the inner side.
- 3, Coronula diadema, shell, seen from the outside; 3 a, scutum and tergum joined together by the opercular membrane, seen from the outside; 3 b, scutum cleaned and enlarged, seen from the inside.
- 4, Section, in a vertical plane, through the skin of a whale, on which a Coronula diadema had been attached, but has been wholly removed: the two curved, horn-like projections occupied two of the eighteen cavities on the under side of the shell, formed by the folded walls: the blacker part is the epidermis; the lighter part is the yellowish fibrous tissue of the skin under the epidermis.
- 5, Coronula reginæ, shell seen from the outside.
- 6, Coronula barbara, internal view of the basal margin and inside of one of the compartments, exhibiting the circumferential transversely looped ends of the folds of the wall, with the inner surface transversely wrinkled.
- 7-9, diagrams, showing how one of the circumferential transverse loops of the wall becomes divided into two transverse loops, thus giving rise to another fold in the wall.
- 10, diagrams, showing how the wall of the young shell in Coronula, from being (a) simply sinuous, becomes deeply folded (b); the folds lastly (c) expanding transversely at their ends, thus giving rise to the circumferential transverse loops, as in fig. 7.