263 [February, 



and form two series of salient angles or tubercles; intermediate rib nearly 

 equal in size, rounded on the submargin of the back, entire. (A cast.) 



Locality. Dallas County. 



2. H. rotundatus. Rounded ; ribs distant, acute, the intervening spaces 

 regularly and profoundly concave; back flattened, with the ribs obsolete and 

 three indistinct longitudinal lines. (Cast.) 



Locality. Dallas County. 



ANCYLOCERAS? D'Orbigny. 



A. approximans. Rounded; ribs acute, oblique, prominent, alternated or 

 bifurcated at the larger end, where there are two distant series of remote 

 tubercles, which are not transversely opposite each other. 



Locality. Arkansas. Prof. Thomas. 



CRIOCERAS, D'Orbigny. 



C. (Ammonceras) Conradi, Morton. This species was described from a 

 single specimen found at Walnford, Ocean Co., N. J. I have since obtained 

 another through the kindness of Miss Wain. It characterizes the lowest part 

 of the cretaceous series. 



CAPRINA. 



C quadrata. Transverse subquadrate, three of the sides flattened, slightly 

 furrowed in the middle. 



Locality. Alabama. Jos. Jones. 



CARDIUM. 



Subgenus Protocardia. 



Cardium Arkansense. Cordate, profoundly ventricose, inequilateral ; umbo 

 and summit very prominent ; disk with minute radiating lines ; posterior side 

 cuniform, extremity nearly at equal distance between beak and base. 



Locdlily. Arkansas. Prof. Thomas. 



Eocene polyp. 



DENDROPHYLLIA ? 



Subgenus Petrophyllia, Conrad. 



Corallum not cellular, but in layers like the coats of an onion ; branches 

 anastomosing; central axial star having distant septa between the lamellae. 



D.? {Petrophyllia) Arhansensis. Corallum minutely granulated, suboval, 

 sides faintly marked with vermicular lines; calicles round, not very prominent, 

 unequally distributed, proximate or remote; lamellae minutely serrate. 



Locality. White River, Arkansas. Prof. Thomas. 



Madrepora vermiculosa, Con., belongs to the genus Dendrophyllia, but not 

 to the above subgenus. 



Eocene onultiv aires. 



CHITON. 



1. C. antiquics. Terminal valves subtriangular, acutely rounded at base or 

 subangulated, punctate, and with minute radiating impressed lines. 



Locality. Claiborne, Alabama. 



This species is named in the Appendix to Morton's "Cretaceous group," but 

 the description is now first published. 



2. C. Eocenensis. Terminal valve rather acutely rounded at base ; ribs 18 

 or 19, rounded, unequal, a few divided by an impressed line nearly their entire 

 length, a few divided only near the base; surface obsoletely punctate or granu- 

 lated. 



Locality. Claiborne, Alabama. 



These two species are only known by their terminal valves, and are very rare. 



