390 CONTRIBUTIONS TO CANADIAN PALEONTOLOGY. 



subovate, longer than broad and broadest in advance of the midlength, 

 but conoavely and shallowly emarginate in the middle in front (when 

 adult), and attenuate behind, the marginal outline being quite petaloidal. 



Ventral valve with a straight, erect slender beak, which is subangular 

 on each side, its apex truncated and perforated, its deltidial area narrow 

 and bounded by two slightly divergent lines. Dorsal valve a little shorter 

 posteriorly than the ventral, with a slightly smaller and entire incurved 

 beak. 



Surface practically smooth, though concentric lines of growth are visible 

 in some specimens when examined with a lens : shell structure minutely 

 punctate. Characters of the interior of the valves unknown. 



Dimensions of an apparently adult specimen : maximum length, 10'8 

 mm.; greatest breadth, 70 mm. ; maximum thickness, 3'8 mm. 



Apparently not very uncommon at Thedford and Bartlett's Mills, in 

 the " Middle third of the section." Speciuiens in the Museum of the Survey 

 were collected at one or other of these localities by the Rev. Hector 

 Currie and Rev. J. M. Goodwillie in 1882, and by Mr. Kernahan in 

 1896. The writer is informed by Mr. Schuchert that he has seventeen 

 specimens of this species from these localities. 



Cran/ena Romingeri, Hall. 



TerihriiUdii Romingeri, Hall. 1863. Sixteenth Rep. N. York St. Cab. Nat. Hist., p. 48, 



figs. 22 & 23. 

 Tercbnilula. Rominrjeri, Hall. 1867. Pal. N. York, vol. IV., p. 389, pi. «0, figs. 17-2.''i, 



C6 & 67. 



Nettelroth. 1889. Kentucky Fossil Shells, Mem. Kent. Geol. 



Snrv., p. 15.5, pi, 16, figs. 20-22. 

 Cranmia Rominrjeri, Hall and Clarke. 1893. Pal. N.York, vol. VIII., pt. 2, p. 297, fig. 

 215 ; and pi. 80, figs. 13-19. 



Same horizon and localities as for the last species. It seems to be 

 rather abundant at Thedford, where it was first recognized by Mr. 

 Schuchert. 



Tropidoleptus carinatus, Conrad. (Sp.) 



Strophomcna cariiiata, Conrad. 1839. Tliird Ann. Rep. N. York Geol. Surv., p. 64. 

 Tropidoleptus earinatus. Hall. 1857. Tenth Rep. N. York St. Cab. Nat. Hist., p. ISl, 



figs. 1 & 2 : & (18,59) Twelfth do., p. 31, figs. 1-4. 

 .. M Rogers. 1858. Geol. Pennsylv., vol. II., pt. 2, p. 828, fig. 672, 



Hall, 1867. Pal. N. York, vol. IV., p. 407, pi. 62, figs. 2 & 3. 



Meek and Worthen. 1868. Geol. Surv. Illinois, vol. Ill, p. 427, 

 pi. 13, fig. 2. 

 M Rath bun. 1874. Bull. Bufltalo Soc. Nat. Sc, 1, p. 254, pi. 9, 



figs. 1, 9, 10, 26. 



