20 Hill Paleontology of the Trinity Division. 



1. That there is not a single invertebrate species in the Trinity 

 Division of exclusive Jurassic age, which would justify placing 

 the beds in that period. 



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

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

 Monopleura, occur only in the Cretaceous. Hence the beds are 

 Cretaceous. 



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

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

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

 tain none of the characteristic upper or middle Cretaceous 

 forms. 



Finally it may be stated that from the above comparison of 

 the life of the Trinity Division with 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. 



FORAMINIFERTE. 



Patellina texana (Roemer). 



Plate I, Figs. 2 (copied after Roemer), 2a, 26, 2c, 2<L 



Orbitidites texana Roemer. Die Kreidebildungen von Texas, 

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



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

 orbiculate, shield-shape, convex above, obtusely conical ; central 

 eminence umboniform, ornamented with close, fine, concentric 

 stria3, otherwise smooth ; lower part fiat, slightly concave, with 

 irregular, radiating, granular ruga), as if perforated by worms. "- 

 Roemer. 



Roemer said: "This species certainly belongs to that group 

 of Lamarck's genus Orbittditex, which D'Orbigny separated as a 

 distinct genus Orbitoliiia." Careful microscopic study of the 

 interior structure by the writer shows the granular structure 

 illustrated in figs. 2a, 26, and that it belongs to the genus 

 Patellina of Williamson. 



