150 PALEONTOLOGY OF NEW YORK. 



ton. The Crania ? Columbiana, Walcott, from the primordial beds of the Mt. 

 Stephen section, British Columbia, is thus referred from external characters 

 only ; the imperfectly known fossil described in vol. i of the Palaeontology of 

 New York (p. 28), as Orhicula deformata, from the Chazy limestone, has an 

 exterior suggestive of Crania, but may be a discinoid. The earliest clearly 

 defined species are C. Trentonensis, Hall, and C seiigera, Hall, from the Trenton 

 fauna; throughout the PaljBOzoic the genus fails to reach a very abundant 

 development in species, though in some faunas these species were very prolific 

 in individuals. The number of recognizable species now known from American 

 palaeozoic rocks will not exceed thirty. 



A few words are necessary in regard to the type-species of Crania. Accord- 

 ing to Dall,* Eetzius confounded under the name C. Brattensburgensis, the 

 Numulus Brattensburgensis of Stobceus, 173i, the Anomia craniolaris of Linne, 

 1760, and a recent species believed to be the Patella anomala of MI'Ller, 1776. 

 Davidson adopted the term C. Brattensburgensis, Stoboeus, not Retzius, as the 

 typical species, but as it has been conceded by most authors that this is iden- 

 tical with Linne's Anomia craniolaris, Dall would make the latter stand as the 

 designation of the type on the ground that Stobceus was not a binomial author. 

 Under the discussion of the genera Discina, Orbiculoidea, etc., attention has 

 been called to the fact that the Orbicula of Cuvier, established on the Patella 

 anomala of Muller, is a synonym for Crania wherever used by authors in the 

 Cuvierian sense. The Orbicula of Sowerby, 1822, and wherever the term has 

 been used by other authors with the same meaning, is synonymous with "Dis- 

 cina" (= Orbiculoidea, D'Orbigny). 



The term Choniopora was applied by ScHAUROTHf to a Permian fossil 

 considered by him as representing a new generic form of Bryozoan. It 

 was subsequently shown by GeinitzJ that the fossil to all external appearances 

 is a Crania with radiately striated and granulated surface, and was described 



* Bulletin Museum Comparative Zoology, vol. iii, No. 1, p. 30. 



t Zeitschr. der deutsch. geolog. Gesellschaft, vol. vi, p. 546. 185 J. 



X Dyas, Heft. I, p. 109. 1861. 



