20 Hill — Paleoidolo(jij oj the Tr'nutij Division. 



1. Tluit tlicre is not u single invcrteln'ate species in tlie Trinity 

 Division of exclusive Jurassic age, wliicli would justify placing 

 the Ijcds in that i)eriod. 



2. The genera all occur in the Cretaceous formations of the 

 rest of the world, and many of them, such as Eequienia and 

 Monopleara, occur only in the Cretaceous. Hence the heds are 

 Cretaceous. 



3. The beds of the Trinity Division are of lowest Cretaceous 

 age, Neocomian, because the genera all occur in the Neocomian 

 or lowest Cretaceous of other countries, and because they con- 

 tain none of the characteristic upper or middle Cretaceous 

 Ibrms. 



Finally it may be stated that from the alcove comparison of 

 the life of the Trinity Division Avith the Cretaceous life of Europe 

 it is evident that it shows not only a resemblance, but a re- 

 markable homotaxial similarity with the Lower or Neocomian 

 of that country, the lowest faunas resembling the Wealden or 

 Lower Neocomian, and the Upper Glen Rose beds the Middle 

 and Upper Neocomian, especially as developed in the region of 

 the Jura and in Spain and Portugal. 



v.— DESCRIPTIONS OF SPECIES. 



F0RAMINIFER.T3. 



Patellina texana (Roemer). 



Plate I, Figs. 2 (copied after Roemer), 2«, 26, 2c', 2d. 



OrbUaUtcs texana Roemer. Die Kreidebildungen von Texas, 

 p. 86, plate x, figs. 7a, 6, c, d. 



" Shell minute, attaining one-eighth of an inch in diameter ; 

 orbiculate, shield-sha{)e, convex al)ove, obtusely conical ; central 

 eminence umboniform, ornamented with close, fine, concentric 

 stria% otherwise smooth ; lower part tlat, slightly concave, with 

 irregular, radiating, granular ruga\ as if })erl'orated by worms." — 

 Roemer. 



Roemer said : " This si)ecies certainly l)elongs to that group 

 of Ivamarck's genus Orhitidltes, which D'Orbigny se^jarated as a 

 distinct genus Orbitolliui.'' Careful microsco[)ic study of the 

 interior structure by the writer shows the granular structure 

 illustrated in figs. 2«, 2b, and that it belongs to the genus 

 Patellina of Williamson. 



