- Fig. 1 a, Pyrgoma grande; 1 b, scutum and tergum, calcified together,
external view of; 1 c, scutum and tergum, internal view of;
1 d, the two scuta and terga, external view, seen from above, having their natural position, when closed.
- 2 a, Pyrgoma milleporæ, shell viewed from above; 2 b, internal view of, showing the sheath; 2 c, scutum and tergum, united, external view of; 2 d, scutum, var. external view of; 2 e, scutum, internal view of; 2 f, tergum, internal view of.
- 3 a, Pyrgoma dentatum shell, external view of;
3 b, scutum, var. 1, external view of;
3 c, tergum, var. 1, external view of;
3 d, tergum, var. 2, external view of;
3 e, scutum, var. 3, external view of;
3 f, tergum, var. 3, external view of;
3 g, scutum and tergum, var. 1, joined together, internal view of.
- 4 a, Pyrgoma crenatum, scutum, external view of, showing the
great depending adductor plate and large occludent ledge; 4 b, external view of.
- 5 a, Pyrgoma monticulariæ, external view of; 5 b, another specimen, internal view of; 5 c, another specimen, external view of; 5 d, portion of circumference of shell, viewed externally, much magnified,
showing the outer lamina, and the irregular, longitudinal septa; 5 e, another specimen of the same, with the longitudinal septa more regular; 5 f, scutum and tergum completely calcified together, external view of.
- 6 a, Creusia spinulosa, shell, seen from above.
- 6 b, 6 c, Creusia spinulosa, var. 1, scutum and tergum, internal view of; 6 d, scutum and tergum, joined together, external view of.
- 6 e, 6 f, 6 g, Creusia spinulosa, var. 2, 6 e, scutum, internal view; 6 f, tergum, internal view of; 6 g, tergum, of another specimen, internal view of.
- 6 h, Creusia spinulosa, var. 3, scutum and tergum joined together, external view of.