306 H. T. Hill — Texas Section of American Cretaceous.. 



between the Fredericksburg division and the undoubted Car- 

 boniferous, are the shore detritus of the Mesozoic sea when 

 it bordered upon the Carboniferous continent. The lowest ma- 

 rine fauna of this division is seen in Parker county and careful 

 study of the same may prove Jurassic affinities. 



Several years of most careful study of the stratigraphy of the 

 whole of the Comanche Series fully confirms its position to be 

 lower than the strata of the Lower Cross Timber beds, which 

 Shumard, White and other authorities have asserted to be iden- 

 tical with the Dakota Sandstone of Meek and Hay den, and 

 hence lower than any of the hitherto described marine groups 

 of the American Cretaceous. The fossils of the upper division 

 are in most cases well preserved, and the species readily distin- 

 guishable. Those of the lower division are very poorly pre- 

 served, especially the bivalve mollusca, the shell structure hav- 

 ing been destroyed, rendering it exceedingly difficult to ob- 

 tain even the generic characters. 



There is an apparent continuity of interlocking faunas 

 throughout the series, and a few forms, such as Cardium (Pro- 

 tocardia) hillanurn and its allies, Neiihea occidentalis Con., and the 

 Oryphcea pitcheri Mort., range throughout. A remarkable fact, 

 however, is that with the exception of the last mentioned fossil, 

 not a single species is known to pass from the Comanche se- 

 ries into the upper formations, and even this is not positively 

 known to do so. The only other fossil which is ascribed to the 

 Upper Cretaceous is the Ammonites pedernalis VonBuch, which 

 has been confounded by some authors with the Placentaceras 

 lenticularis of Meek, a form characteristic of the Upper Creta- 

 ceous of nearly all the world. It is an entirely different spe- 

 cies however, as has been shown by Mr. Meek. Another remark- 

 able feature of the fauna of the Comanche series is that the 

 species have no affinities or resemblances in the other Creta- 

 ceous formations of the United States, while, on the other hand, 

 they present remarkable analogies to certain well-known forms 

 of other countries, especially eastern Europe and tropical Amer- 

 ica. This fact has always been so apparent, that many of the 

 authors of species described from Texas (none of whom save 

 Jules Marcou suspected their true paleontologic horizon), 

 frankly confessed that they could distinguish no difference be- 

 tween the American and European forms, and gave them the 

 same names, as in the case of the Ostrea diluviana Linne, White, 

 the Gryphcea sinuata, var. Americana Marcou, and many of 

 Koemer's and Shumard's species. The new names bestowed 

 upon other forms were accompanied by expressed doubts as to 

 their value, while nearly all the authors gave such close analo- 

 gies that modern biologists would not hesitate to consider the 

 differences varietal, and not specific. 



