462 DILLER AND STANTON THE SHASTA-CPIICO SERIES. 



which in a general way makes the Potomac equivalent to a part of the 

 Shasta portion of the Shasta-Chico series, is greatly strengthened hy Pro- 

 fessor Fontaine's study of the flora. Of the twenty-two species of plants 

 found in the Shasta beds, four, viz., Dioonites buchianus, var. Angustl- 

 folms, Abietites angusticarpus, Sagenopteris latifolia- and Aspidium hetero- 

 phyllam, have been determined as certainly identical with forms found 

 in the Potomac. The one first named is the most abundant plant in the 

 collection from the Shasta beds. Besides these, ten other species have 

 been determined as probably identical Avith Potomac forms. If not iden- 

 tical they are at least closely related forms. Of some of these forms Pro- 

 fessor Fontaine remarks that their identity is marked (?), not because he 

 had any doubt in the matter, but because the amount of material was 

 too small to justify a positive opinion. 



COMANCHE SERIES OF TEXAS CRETACEOUS. 



This series, consisting mainly of limestones, which has a very great 

 development in Texas and Mexico, underlies the equivalents of the 

 Upper Cretaceous of the Rocky Mountains and Great Plains regions, and 

 therefore holds the same stratigraphic position as the Shasta portion of 

 the Shasta-Chico series. According to Mr R. T. Hill,"^ the lower portion 

 (Trinity division) of the Comanche has an invertebrate fauna related to 

 the Neocomian of Europe, and consequent^ of the same age as a part of 

 the Shasta fauna, although these two faunas seem to have nothing in 

 common, and if they were strictl}^ contemporaneous must have been 

 separated by a great land barrier, as White has suggested. The fossil 

 plants furnish more direct evidence for this correlation. The Glen Rose 

 beds, about 250 feet above the base of the Trinity division, have yielded 

 a flora, described by Professor Fontaine,t that is very closely related to 

 that of the older Potomac and contains one species certainl}^, and two 

 others doubtfully, identified by Professor Fontaine in our recent collec- 

 tions from the Shasta. 



The most promising field for the discovery of the direct relations of the 

 Shasta to the Comanche is in southern Mexico, where it seems probable 

 that portions of both series may yet be found together or their faunas 

 intermingled. The Comanche series is known to cover a large part of 

 Mexico, and the Shasta-Chico series certainly extends as far south as 

 29° 30' on the Pacific coast. The Ammonites described by Dr J. Felix X 

 from the Neocomian near Tlaxiaco, state of Oaxaca, are related to some 

 of those from the Knoxville beds, while those from Tehuacan, in Pueblo, 

 seem to belong to the Comanche fauna. 



*Proc. Biol. Soc. of Washington, vol. 8, 1893, p. 20. 

 fProc. U. S. Nat. Mus., vol. IG, 1893, pp. 261-282. 

 X PalfBontographica, vol. 37,1891, pp. 180189. 



