30 Hill Paleontology of the Trinity Division. 



Pholadomya knowltoiii sp. nov. 

 Plate II, Figs. 1, 2. 



Choffat (Materiaux p6ur L'Etude Stratigraphique et Paleon- 

 tologique de la Province D'Angola, Geiievji, 1888, p. 84, plate v, 

 figs. 1-3) describes under the name of P. pleufomyseforrw.8 a form 

 indistinguishable from this species. His description, as follows, 

 corresponds fully with our species : 



" Equi valve, inequilateral ; swollen below the beaks ; anterior 

 borcle^ rounded and completely closed ; posterior border com- 

 pressed at the extremity, which is slightly turned upward, trun- 

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

 and in contact with each other; cardinal portion of anterior 

 border sloping and its continuation strongly rounded; the pos- 

 terior cardinal border straight, slightly elevated to its extremity ; 

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

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

 marked by irregular longitudinal plications." Choffat. 



This shell can in no way be distinguished from the excellent 

 figures and descriptions given by Choffat of Pholadomya plenro- 

 myseformtSj from Dombey, on the west coast of Africa, where a 

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

 their identity cannot be positively established without compari- 

 son of specimens. The faint grooves from beak to pallial border 

 are not brought out well in our figures. 



The form first appears in America in the medial portion of 

 the (lien Rose beds of the Colorado river section, near the mouth 

 of Bull creek, and again appears in the supposed Caprina lime- 

 stone at Austin, in the Fredericksburg Division. 



Pholadomya lerchi sp. nov. 

 Plate IV, Fig. 3. 



Outline subpyramidal in lateral aspect ; length, 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 pal- 

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

 margin a continuous curve with the anterior margin, and rapidly 

 increasing in curvature posterior ward, terminating obtusely with 

 the truncated posterior margin; posterior margin sharply trun- 

 cate, about one inch in length ; anterior umbonal margin very 

 short, marked by a small depression immediately below the 



