P. linguatula.
P. lamellosa. The lamellous Petricola. Pl. [7], fig. 3.
Species oval, trigonal, radiated; two teeth on one valve, and one on the other.
P. pholadiformis. The Pholas-shaped Petricola.
Species transversely elongated.
3. Venerirupis. Seven species.
Another lithophagous shell, taken from the genus Venus, from which it is distinguished by the different disposition of the teeth, having three primary in one of the valves at least.
Shell more or less irregular, sub-trigonal, striated or radiated, equivalve, inequilateral, the anterior side shorter and rounded, the posterior sub-truncated; summits well marked; hinge sub-regular, more or less dissimilar, formed by slender, narrow, cardinal teeth, variable in number on each valve, sometimes two on the right and three on the left, and sometimes three on both; these teeth are small, contiguous, parallel, and but little, if at all, divergent exterior; very weak.
Venerirupis perforans.
V. nucleus.