150 
PALAEONTOLOGY 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. 23), as Orbicula 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. setigera, Hall, from the Trenton 
fauna; throughout the Palaeozoic 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,* Retzius confounded under the name C. Brattensburgensis, the 
Numulus Brattensburgensis of Stobgeus, 1732, the Anomia craniolaris of Linne, 
1760, and a recent species believed to be the Patella anomala of Muller, 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 Stobgeus 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 Geinitz^ 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. 1851. 
t Dyas, Heft. I, p. 109. 1861. 
