860 DHE JOORNALNOLNGIZOlO GNA 
argillaceous shales. A single form of Aucella (A. dronunz) is the only 
species that it has in common with the overlying division. Its fauna 
is very rich in Ammonites, especially in the genus Perisphinctes, of 
which sixteen species are recognized. ‘The other Ammonitic genera 
represented are Rhacophyllites, Haploceras, Olcostephanus, Hoplites. 
and Aspidoceras. 
After discussing the somewhat discordant evidence of the fossils 
the writers conclude that this lowest fossiliferous bed should be 
referred to the upper Jurassic, while the upper division of No. 2, in 
which Aucelle are so abundant. are believed to be Neocomian. 
This important contribution to American Mesozoic palzontology,. 
derives its chief interest from the bearing that it has on the geography 
of the continent during late Jurassic and early Cretaceous time and on 
the correlation of the lower Cretaceous fauna of the Pacific coast with 
that of the Texan region. 
It is well known that on the west coast of the United States and 
British Columbia there is a great thickness of lower Cretaceous strata 
(Knoxville and Horsetown beds), characterized byan abundant marine 
fauna. In the Texan region there is another thick series of lower Cre- 
taceous beds (the Comanche series), which is also characterized by a 
large but totally different marine fauna. The Texan facies of the 
lower Cretaceous is known to extend into Mexico and over a large part 
of that country as far west as Arivechi in Sonora. The absence of 
species common to the two faunas seems to indicate that they lived in 
different basins without free intercommunication, and this dissimilarity 
of faunas has prevented exact correlation of the strata. 
Catorce, San Luis Potosi, where Castillo and Aguilera obtained the: 
fossils they describe, is near the tropic of Cancer and in longitude 
101° East, directly south of the principal Texan area of the Comanche 
series, and yet the fauna contain none of the characteristic Comanche 
types, but is related to the Pacific coast faunas. This relationship is: 
especially shown by the abundanee of the genus Aucellawhich is essen- 
tially characteristic of the boreal and Pacific regions, though it is occa- 
sionally found outside of those areas. The forms of Aucella, figured from 
Catorce, though listed under different specific names, can nearly or 
quite all be duplicated in collections from the Knoxville beds of Cali- 
fornia. ‘The ammonites also show a number of forms closely related 
to those of the Knoxville. The lowest fossiliferous zone at Catorce, 
however, with its numerous species of Perisphinctes, is probably older 
than the Knoxville. The only suggestion of relationship with the 
