30 Hill — PalcoidoliKjij (if the Triniiij l)lvisloii. 



Pholadomya kno-wltoni sp. uov. 



Plato II, Figs. 1, 2. 



Choflat (Materiaux pour L'EtiuIe Stratigrapliiquu et Paleou- 

 toloo-ique de la Province D'Angola, Geneva, 1888, p. 84, plate v, 

 figs. 1-3) describes under the name of P. plcK/roini/n^'onnls a form 

 indistinguishable from this species. His description, as foUoAvs, 

 corresponds fully Avith our species : 



" E(|ui valve, inequilateral ; swollen below the beaks ; anterior 

 l)order rounded and comj)letely closed ; posterior border com- 

 })ressed at the extremity, which is slightly turned upward, trun- 

 cated and slightly gaping ; beaks small, elevated, strongly inflexed 

 and in contact with each other ; cardinal portion of anterior 

 border sloping and its continuation strongly rounded ; the ]^os- 

 terior cardinal border straight, slightly elevated to its extremity ; 

 anterior face blunt, Ijchind which a slight, faint groove extends 

 from the beak to the pallial Ijorder. The surface of the shell is 

 marked b}' irregular longitudinal plications." — Choffat. 



This shell can in no way be distinguished from the excellent 

 figures and descriptions given l)y Choffat of Phulndomya plewo- 

 mucffariiiis, from Doml^ey, on the west coast of Africa, Avhere a 

 fauna closely allied to the Comanche series occurs, but of course 

 their identity cannot be positively established without com})ari- 

 son of specimens. The faint grooves from beak to })allial l)order 

 are not brought out well in our figures. 



The form first appears in America in the medial portion of 

 the Glen Pose beds of the Colorado river section, near the moutli 

 of Bull creek, and again a})pears in the supposed Caprina lime- 

 stone at Austin, in the Fredericksburg Division. 



Pholadomya leichi sp. ikov. 



Plate IV, Fig. 3. 



Outline subpyramidal in lateral aspect ; lengtli, three and one- 

 half inches ; height, two and one-half inches ; greatest thickness, 

 two inches; beak situated at anterior third, of medium propor- 

 tions ; anterior margin semicircular in outline from beak to ])al- 

 lial margin, into which it merges by a continuous curve ; jiallial 

 margin a continuous curve with the anterior margin, and rapidly 

 increasing in curvature })osteriorward, terminating obtusely with 

 the truncated posterior margin ; j)osterior margin sharply trun- 

 cate, aV)out one inch in length ; anterior umbonal margin very 

 short, marked by a small depression immediately below the 



