28 Hill Paleontology of the Trinity Dicixion. 



Eriphyla pikensis Hill. 

 Plate IV, Figs. 4, 5, 6. 



? 



Corbictda pikensis Hill. Arkansas Geological Survey, Annual 

 Ueport 1880, vol. H, |>. W, plate ii, figs, l->, iBa, 1-4, 15, 10, 17. 



This form was originally figured by the writer under the ge- 

 neric name of Corbicula, and is very closely allied to the so-called 

 Qyrena astarteformis Koch and Dunker, from the Wealden. of 

 Germany. Professor Marcou has referred it to the AstoftidK- t 

 but it is undoubtedly a species of the genus Eriphyla of the 

 Astartidre distinguished by the lateral teeth. 



It occurs in great abundance in Pike county, Arkansas, and 

 sparingly at-the plant bed of the Paluxy, near Glen Rose, Texas. 



Requienia texana (?) (Roemer)- 



Caprolina texana Roemer. Kreidebildungen von Texas, p. 80, 

 plate v, figs. 2a, 26. 



A Requienia, provisionally referred to R. texana Roemer, is one 

 of the prominent species of the Glen Rose beds and occurs in 

 massive agglomerate some twenty feet in thickness at Glen Rose, 

 Thorp Springs, Granbury, and in southern Parker county. In 

 Roemer's description he asserts that it is indistinguishable from 

 Requienia lonsdalli D'Orb., of the French Neocomian, except by 

 its thicker shell. It is desirable to closely compare this form 

 with R. patagiata White.* Dr. Roemer says that the latter spe- 

 cies is entirely distinct, the larger valve of R. texana not being 

 so elevated as in R. patagiata. In the abundant material col- 

 lected by the writer this distinction does not always hold good, 

 yet there is a general difference in appearance, especially in the 

 larger size and more rounded character of the valves of the Glen 

 Rose forms, which may make it a distinct species from either of 

 these. The type forms of the R. tc.i'iuia Roemer and the R. 

 patagiata White occur in the horizon which we at present accept 

 as the Caprina limestone, while the Requieniax of the agglomerate 

 at Granbury and at the base of the Colorado section occur 

 several hundred feet below them, and may prove a distinct 

 species. 



is the lowest occurring genus of the aberrant Cham- 



* Itcqnimla pdiayiala White. U. S. Geological .Survey, Bulletin No. -1, 

 p. (>, plate v, iig.s. 1-8. 



