FOSSILS OF THE DOLOMITES 229 



only form worthy of record, and this genus is one which is well repre- 

 sented in the calcareous limestone of the East. The Echinodermata are 

 so unusual, and when present so poorly preserved, that they may be 

 ignored in this place. The Bryozoa are represented by a few forms too 

 poorly preserved for accurate determination, but the commonest form is 

 probably Prasopora., a genus which is one of the most conspicuous in the 

 calcareous Trenton elsewhere. The Brachiopoda have a goodly repre- 

 sentation, the following genera being recorded: Lingula, Platystrophia, 

 Dalmanella, Dinorthis, Orthis, Eafinesquina, Plectambonites, Leptsena, 

 Ehynchotrema, and Cyclospira. All of these genera are present in abun- 

 dance in calcareous formations of essentially the same age as the Galena, 

 and there is no single species in the Galena which does not occur in these 

 calcareous formations. The Pelecypods are represented by nine genera, 

 as follows: Byssonychia, Clionychia, Orthodesma, Cyrtodonta, Vanux- 

 emia, Ctenodonta, and Cuneamya. As in the case of the Brachiopods, 

 all of these genera are typically represented in calcareous beds elsewhere, 

 although one or two of the species recorded have been described exclu- 

 sively from the Galena formation. The Gastropoda constitute the largest 

 single element in the fauna, fifteen genera being recorded, as follows : 

 Bellerophon, Phanerotrema, I^ophospira, Liospira, Clathrospira, Hormo- 

 toma, Coelocaulis, Eccyliopterus, Helicotoma, Ecculiomphalus, Maclurea, 

 Maclurina, Trochonema, Holopea, and Fusispira. A small minority of 

 the species of these Gastropoda have been described from the Galena, 

 and are not as yet recognized elsewhere, but every one of the genera and 

 most of the species are well represented in calcarous formations of similar 

 age. The Cephalopoda are represented by the genera Cameroceras, 

 Orthoceras, Triptoceras, Oncoceras, and Cyrtoceras, and, as in the case of 

 the other groups of organisms mentioned, these, too, are well represented 

 by the identical species in calcareous formations. Only one trilobite 

 genus, Illsenus, is recorded, but this genus, and even the same species, 

 occurs in abundance in contemporaneous calcareous beds. 



From the facts gleaned in sue ha census of the Galena faunas, there 

 seems to be no evidence whatever for concluding that the life conditions 

 in the Galena sea were in any respect different from those of the basins 

 which are now represented by purely calcareous sediments. There is no 

 single characteristic of the fauna which would suggest that the waters 

 were more saline, warmer, or shallower than the seas in which, for in- 

 stance, the Trenton limestone of the East or the Kimmswick limestone 

 of southern Illinois and Missouri were deposited. It is ordinarily con- 

 ceded that an intensification of the salinity of sea waters produces a 



