IN THE NORTHWEST. 



599 



ranging between the Potsdam sandstone and the Niagara limestone; thirty-seven of which may be referred 

 to species distributed through the Trenton limestone, Utica slate, and Hudson River group, as follows : — 

 Chsetctcs lycoperdon } Conularia Trentonense, Ambonycliia undata, A. amygdedina, Nucula levata, Belle- 

 rophon bilobatus, Plcurotomaria lenticularis, P. subconica, P. umbilicata, Subulites elongata, Murchi- 

 sonia subfusiformis, 31. bellicincta, M. tricarinata, Cytoceras macrostomum, Orthoceras vertcbrale, 0. 

 laqueatum, 0. junceum, Lepteena planumbona, L. cdternata, L. sericea, L. deltoidea, Atrypa hemi- 

 plicata, A. modesta, A. capax, Spirifer biforatus, Ortlus testudinaria, 0. iricenaria, Lingida quadrata, 

 Fcltino-encrinites anati/ormis, Hctcrocrinus hcterodacfylus, Calymcne senaria, Isotelus gigas, Illsenus 

 crassicauda, Oeraurus pleurexantliemus, Phacops callicephcdus, and Liclias Trcntoncnsis. 



One species, Gonloceras anceps, is peculiar to the Black River limestone : one, the Orthoceras multica- 

 mcratum, to the Bird's eye limestone ; and one, Maclurea magna, to the Chazy limestone. 



Four appertain to the Clinton and Niagara groups : — Pentamerus oblongus, Atrypa reticularis, Lepteena 

 depressa, Catenipora escharoides. 



Among the species from the Devonian rocks on the Upper Mississippi, between Parkhurst and New 

 Buffalo, and at the other localities in the Northwest, more than two-thirds are identical with species occur- 

 ring in the shell and coralline beds of the Falls of the Ohio, in the vicinity of Louisville, and Charleston 

 landing, Indiana. 



The Onondaga limestone and Hamilton group of New York are represented by the following species : — 

 Lepteena depressa, L. inequistriata, Atrypa reticularis, A. concentrica, A. aspiera, Spirifer macro- 

 notus (?), S. mucronatus (?), S. congesta, Plenrorliynclms trigonalis, Phaceps crassimarginata, P. ma- 

 cropJithalma, and Favosites gothlandica. This list will doubtless be greatly extended, when the forth- 

 coming volumes on the palaeontology of the higher rocks of the New York system appear, as they will 

 afford means of comparison between the fossils of the two districts, not now at our disposal. 



Thirteen species are identical with European forms, as follows : — Lucina proavia, Spirifer licteroclytus, 

 Atrypa reticularis, A. aspcra, A. concentrica, Orthis resvpinata, 0. umbracidum, Clionetes nana, 

 Phacops macrophtlialma, Astreea ananas, A. liexagonum, Stromatopora polymorpha, Favosites gotldau- 

 dica, and Favosites polymorpha. Of these, several belong exclusively to the Devonian strata in that 

 country, while some extend downwards into the Silurian, and some above into the Carboniferous beds. 



Of the one hundred and twenty Carboniferous species collected chiefly in the State of Iowa, twenty-four 

 are European species; these are — Chcetetescapillaris, LitJiostrotion fioriforme, Conularia quaelrisulcata, 

 Clionetes variolata, Orthis umbracidum, 0. Michelini, 0. resupinata, Terebratula plano-sulcata, T. lamel- 

 losa, T. Roissyii, T. sacculus, Productus punctatus, P. cora, P. Flemingii, P. costatus, P. scmireticu- 

 latus, P. carbonarius, Spirifer striatiis, S- cuspielatus, S. lincatus, S. rotundatus, Fusulina cylindrica, 

 Platycrinus gramdatus, and Potcriocrinus plicatus. 



It is remarkable, that, while more than one-half of the Brachiopoda of this system can be referred to 

 European species, only two out of the fifty-two Crinoids (described and undescribed), have been recog- 

 nised as common to the two countries. 



From the foregoing, it appears, that the Brachiopoda of these western palseozoic groups embrace the 

 greatest variety of species : the Silurian period furnishing the greatest number of this order ; the Carboni- 

 ferous next ; while the Devonian rocks have as yet supplied the fewest. This is partly to be accounted 

 for, however, from the limited area over which this latter group of rocks is accessible. The Crinoidea 

 rank next to the Brachiopoda, in the abundance of species ; about nine-tenths of these are from beds of 

 the Carboniferous age. 



Next to the Crinoidea, in numerical importance, come the Crustacea ; this order being by far the most 

 numerous in the Silurian period, which has furnished four-fifths of the whole number of species. The 

 Cephalopoda and Gasteropoda are next most abundant ; the latter system affording the greatest amount 

 of species. 



The Polyparia, on the other hand, appear to be most abundant in the Devonian rocks ; indeed, some 

 of these beds, in Iowa, are made up almost entirely of corals. The Acephala appear to be most abundant 

 in the Silurian and Carboniferous rocks. Only two or three species of Pteropoda have as yet been found, 

 two of which appear in the Silurian rocks, and one in the carboniferous, which formations have afforded the 

 only species of Foraminifera yet obtained. 



If we may judge from the abundance of coralloid limestones in the Devonian period, and the purity of 

 these calcareous beds, with little siliceous and argillaceous intercalations, we are perhaps justified in con- 



