The fossil fish of these Richmond strata belong to the liassic genus Tetragonolepis, and to a new genus which I have called Dictyopyge. Shells are very rare, as usually in all coal-bearing deposits, but a species of Posidonomya is in such profusion in some shaley beds as to divide them like the plates of mica in micaceous shales (see [fig. 317.]).
Fig. 317.
- a. Posidonomya.
- b. young of same.
Oolitic coal-shale, Richmond, Virginia.
In India, especially in Cutch, a formation occurs clearly referable to the oolitic and liassic type, as shown by the shells, corals, and plants; and there also coal has been procured from one member of the group.