GENEEAL OBSERVATIONS. 17 



ten, monomynrian Conchifera ; two, dimyarian Concliifera ; six, Gaster- 

 opoda ; and three, Cephalopoda. The two species of Echinodermata do 

 not, however, correctly represent the relative prevalence of that class, 

 because the geologists of the expedition report the presence of scattered 

 joints of Crinoids at almost all the localities, but which, being of little value 

 for classification, were not collected. Of these sixty-two species, thirty- 

 nine are more or less frequently met with in strata of the Carbonifei'ous 

 period in the States bordering upon the Mississippi Rivei'. 



Although the faunal characteristics of the period are so clearly and 

 fully shown in the collections, the floi'a of the period, so abundant in the 

 States eastward, has very slight representation among them. Indeed, the 

 collection contains only a single specimen each of Sigillaria and Neuropteris ; 

 the former from White Pine, Nev., and the latter from Cedar Creek, 

 Maricopa County, Ariz. 



PERMIAN PERIOD. 



The collections contain no fossils that I have definitely refen'ed to the 

 Pei'JTiian period. A few imperfect specimens were collected from a porous, 

 apparently magnesian, limestone, near Jacob's Pool, Arizona, which is prob- 

 ably at the very summit of the Carboniferous series. One of the species 

 only was satisfactorily recognized, and that is referred to BaheveUia parva 

 Meek and Hayden. The collections also contain specimens apparently 

 identical with that species from strata near Camp Wingate, N. Mex. The 

 strata are probably equivalent at the two localities. 



MESOZOIC. 



TEIASSIC PERIOD. 



So far as can be determined, none of the invertebrate fossils contained 

 in the collections are properly referable to the Triassic period. 



JURASSIC PERIOD. 



The collections contain only eight species in all that I have referred to 

 the Jurassic period. All of these were nowhere found associated together 

 in the same strata ; consequently the fauna of the period was nowhere found 



2 F 



