312 GEORGE H. GIRTY 
Guadalupian includes two formations, the Delaware Mountain forma- 
tion and the Capitan limestone. The Delaware Mountain formation 
consists of sandstones and limestones, largely arenaceous to the North 
and largely calcareous to the South. The Capitan consists of whitish 
limestones and dolomites. ‘Thus constituted the Guadalupian series 
is about 4,000 feet thick. The faunas of the two divisions of the 
Guadalupian are closely related to one another. They are very 
rich and varied, having already furnished over 325 species. ‘The 
Guadalupian fauna is peculiar. But few of its species are com- 
mon to the other American faunas and some of its genera, such as 
Richthofenia, Leptodus, Geyerella and Aulosteges, have not been noted 
elsewhere in the western hemisphere. Even the more common genera 
are in many cases represented by uncommon types. As an instance 
may be mentioned the genus Composita (Seminula), which, by the 
way, seems to be rather characteristic of our American faunas where 
it is ever present and ever abundant. In the Guadalupian this 
genus develops a bi-lobed species with a sinus on the dorsal as well 
as on the ventral valve and a deeply emarginated anterior border. 
It is possible that the Guadalupian fauna may have an equivalent 
in California in the Robinson formation, in which I have noted a 
species of Lepiodus, and a suggestion is contained in some forms from 
Nevada, but aside from this the Guadalupian facies is known only in 
a limited area in New Mexico and Texas. 
It remains to speak of still another western fauna having a pro- 
nounced facies, a wide distribution, and a range through a consider- 
able thickness of rocks. I mean the fauna of the so-called Permo- 
Carboniferous of the Wasatch Mountains, and the Permian of Mr. 
Walcott’s Grand Canyon section. This fauna, which ranges also into 
Wyoming and Idaho, comprises little else than pelecypods, of which 
Myalina and Aviculipecten are the most common types, the Pectinoids 
being especially abundant and varied. It may tentatively be corre- 
lated with the Guadalupian (Delaware Mountain division), athough 
it presents but little resemblance to the Guadalupian fauna as at 
present known. At least, it appears to occupy a corresponding 
position in the section, resting upon strata which in the light of our 
present knowledge are correlated with the Hueco formation. 
These western faunas are more easily correlated with those of 
