a new genus of Fossil Shells. 485 



9. Pachyodon attenuatus, n. s., Plate X. fig. 13, 14. 



Shell cuneiform ; transverse diameter twice its height ; posterior 

 end strongly attenuated ; lunule small but deep ; transverse diameter 

 2-8, height 1-4, thickness 0-7. 



Lias, Battledown, near Cheltenham. 



Museum of Bristol Institution. 



For an extended suite of this elegant species I am indebted 

 to my excellent young friends Messrs. Buckman and Murley 

 of Cheltenham, and I would gladly have availed myself of 

 the opportunity of attaching their names to this and another 

 species, but from the feeling, that character alone can be le- 

 gitimately used for specific names. 



10. Pachyodon concinnus, Plate X. fig. 15, 16. 



Shell smooth, transversely oblong, ovate, anterior portion produced; 

 lunule deep ; lines of growth distant with intervening lines ; basal 

 margin convex ; height 2*0, length 4"5, thickness 0'9. 



Lias, Langar, Nottinghamshire ; Saltford and Weston, near Bath. 



Unio concinnus, Sowerby, Min. Conch., tab. 223. fig. 1, 2. 



, Goldfuss, p. 181. pi. 132. fig. 2. a b. 



Museum of Bristol Institution, Samuel Worsley, Esq. 



This elegant species has the anterior (posterior of Sowerby) 

 margin considerably more extended than is exhibited by the 

 figure in the ' Mineral Conchology.' 



Casts of the interior are common in the lias at Saltford and 

 Weston, near Bath. (Vide Walcott's Fossils near Bath, fig. 4.) 



11. Pachyodon ovalis, n. s., Plate X. fig. 17. 18, 19. 



Shell elliptical ; anterior margin rounded, posterior margin but 

 little attenuated ; the lunule or depression of the anterior dorsal part 

 small and narrow ; height 1"1, length 1*7, thickness 0*6. 



Lias, Frethern, Gloucestershire. 



Museum of Bristol Institution. 



Of this species there is a singular rugose variety (fig. 19.) 

 which deserves especial notice, and were it not for the inter- 

 vention of H. E. Strickland, Esq., I should have described it 

 as a distinct species under the name of P. rugosus ; but from 

 an examination of a large number of specimens, he is con- 

 vinced the rugose and crumpled character depends upon a 

 crushing under pressure subsequent to interment. 



In addition to the species above described, I have seen two 

 individual specimens, which I think, \ipon further examina- 

 tion, will prove distinct — one in the Bristol Institution collec- 

 tion, the other in the possession of II. E. Strickland, Esq. 



