Cincinnatian and Lexington Fossils 73 



the umbonal ridge is 5.5 mm. The distance of the beak from the 

 posterior end of the shell, as far as preserved, is 3.5 mm. The 

 distance from this posterior end of the shell to the ventral margin 

 at the umbonal ridge is about 6.3 mm. The ventral margin makes 

 an angle of about 35° with the hinge-line. 



Since only a single specimen of this species is known, it may 

 be necessary to modify this description eventually, but the speci- 

 men is suiificiently distinct from all others hitherto described to 

 make its chief characteristics apparent. 



Conocardiuni richniondensis was found 15 feet below the 

 Clinton or Brassfield limestone, on Elkhorn creek, three miles south 

 of Richmond, Indiana, associated with Beatricea imdulata, Strep- 

 telasnia vagans, Coliimnaria alvcolata, Columnaria vacua, Heher- 

 tella sinuata, Platystrophia acutilirata, Platystrophia nioritura, 

 Schizolopha tropidophora, Helicotonia inarginata, and Ischyro- 

 donta ovalis. The conspicuous Ischyrodonta layer occurs immedi- 

 ately above. 



Conocardiiim iuunatnruin, Billings, from the Black River 

 limestone at Paquette Rapids, on the Ottawa river, has a much 

 broader umbonal region marked by numerous radiating striae. 



Clidophorus, sp. 



(Plate I, figs. S A, B.) 



A species of Clidophorus occurs in the Saltillo bed, at Qifton, 

 Tennessee, which closely resembles Clidophorus neglcctns, Hall, 

 from the Maquoketa shales of the upper Mississippi basin, but the 

 umbonal ridge is less angular, the posterior outline is more rounded, 

 and the clavicle, instead of sloping backward, slopes forward, leav- 

 ing a shorter anterior muscle scar. It probably is a new species, 

 but difficult to differentiate from some of those already defined. 



Suecoceras inaequabile, Miller, 



(Plate I, figs, i, 2.) 



Endoceras inaequabile was described by S. A. Miller from the 

 Richmond group at Bristol, Illinois. It consists of the lower end 

 of the siphuncle, showing the impressions of the septal necks as 

 far as the tip, indicating that the nepionic bulb had been completely 

 incorporated into the phragmocone. These impressions are in- 

 clined away from the apical end and toward the straight side of 

 the nepionic part of the siphuncle. 



A similar specimen was found at Clarksville, Ohio, in the 



