SYNOPSIS OF GENERA. xli 



senting an aspect unlike most other Lamellibranchiata, and in some aspects 

 having much the appearance of a bivalved crustacean. 



From our present knowledge of these fossils they appear to form a peculiar 

 group, which may be termed Prothyridae. 



Examples : Prothyris lanceolata, pi. Ixxvi, figs. 2-8. 



Prothyris planulata, pi. Ixxvi, fig. 1; pl. xciv, fig. 8. 

 Prothyris data, pl. xciv, fig. 7. 



Solemya, Lamarck (Hist, v, p. 488; 2d edition, vi, p. 123. 1818). 



[Type, S. Australis — a recent shell.] 



Shell equivalve, inequilateral, transversely elongate, obtuse at the extremi- 

 ties. Epidermis shining, extending beyond the margin of the shell. Beaks 

 not prominent, scarcely distinct. A cardinal tooth in each valve, dilated, com- 

 pres.sed oblique, sub-concave on the upper side to receive the ligament. Liga- 

 ment in part internal and in part external. 



Prof. King (Monograph of the Permian Fossils of England, p. 177) has pro- 

 posed the generic name Janeia for the fossil species before referred to Solemya. 

 At a later period, however (in the appendix, pages 246, 247), he has given the 

 result of some further observations upon the recent and fossil species of the 

 genus, and concludes that the latter are true Solemya, and gives an emended 

 diagnosis of the genus. 



The European fossil species of the genus occur in the Devonian of the Eifel, 

 in the mountain limestone of England, and in the Permian of Russia and of 

 England. 



Example : Solemya vetusta, pl. xlvii, figs. 53-55 ; pl. xciv, fig. 10. 



Tellinopsis, Hall (Prelim. Notice Lamellibranchiata, 2, p. 80. 1869-70). 

 [Type, Nuculites subemarginata, Conrad.] 



Shell equivalve, sub-equilateral, sub-elliptical. Anterior end rounded. Pos- 

 terior end sub-truncate or emarginate. Beaks small, not prominent. Cardinal 

 line gently curved. Umbonal slope prominent and defined above. 



