BRACHIOPODA. 
121 
1884. Discina, Worthen. Bulletin No. 2, Illinois State Museum Natural History. 
1884. Discina, White. Thirteenth Ann. Rept. State Geologist Indiana. 
1884. Discina, Walcott. Palaeontology Eureka District. 
1885. Discina, Clarke. Bull. No. 16, U. S. Geological Survey. 
1888. Orbiculoidea, Herrick. Bull. Denison University, vol. iv. 
From the lack of proper apprehension of the type-species of the genera 
Discina, Orbicula and Orbiculoidea, there has long been, and still exists great 
confusion among authors in the application of these terms. The zealous 
endeavors of Mr. W. H. Dall* to unravel the complications in which these 
genera are involved, and to clear away the uncertainty in regard to the specific 
values of the types, ought to go far toward removing the general reluctance to dis¬ 
turb the currency of some of these terms, especially Discina, a name in almost 
universal use for forms confessedly not congeneric. The rectifications required 
in such a case as this are of so fundamental a nature as to cause a certain 
disquietude, but such instances serve to emphasize the necessity for the enforce¬ 
ment of the rule too often violated, that the application of a generic name 
must be in harmony with the characters of the type-species. 
The genus Discina was described by Lamarck in 1819, f and the typical 
example taken, D. ostrceoides, Lamarck, of which neither figure nor description 
was given. It appears from observations by Reeve, £ that the original specimen 
used by Lamarck was obtained from Mr. J. de C. Sowerby, and Dall observes§ 
that it “ is the same species and from the same lot of specimens, as the shell 
described by Mr. G. B. Sowerby in the Linnean Transactions, and well figured 
by him there under the name of Orbicula Norvegica. His very excellent figure 
enables me to speak with positiveness in saying that it is identical with Crania 
radiosa, Gould, of which the type-specimens are before me. The figures of 
Schumacher are sufficiently exact to allow of identifying the species with his 
[Schumacher’s] Crania striata.” But this Orbicula Norvegica of Sowerby|| is 
♦Bull, Museum Comparative Zoology, Harvard College, vol, iii, No. 1. 1871. 
t Histoire Naturelle des Animaux sans vertebres, vol. vi, p: 236. 
J Conchologia Iconica; Mongr. genus Orbicula. 1862. See, also, Revision of the History, Synonymy, 
and Geographical Distribution of the recent Crania; and Orbiculse, in Ann. Nat. Hist., vol. x. 1S62. 
§ Bull. Museum Comparative Zoology, loc. cit., p. 40. 
|| Trans. Linnean Society, vol. xiii, p. 468. 1822. 
