46 AMERICAN JOURNAL 



OBSERVATIONS ON THE GENUS ASTARTE, "WITH 

 DESCRIPTIONS OP THREE OTHER GENERA OF CRAS- 

 SATELLIDiB. 



BY T. A. CONRAD. 



Sowerby described his. genus Astarte from Oolitic shells of 

 which he had specimens not well representing the hinge char- 

 acter. In a collection of shells from the Great Oolite, pre- 

 sented to the Academy by Dr. Wilson, are specimens labelled 

 in Eno-land, of A. elegans, A. lurida and others, in which the 

 hinge character is well exhibited. I propose to give a new 

 diagnosis of the genus, and to figure the hinges of A. lurida and 

 A. elegans, which prove the genus to be distinct from Orassina, 

 Lam. Astarte, as thus defined, became extinct at the close of 

 the Lower Green Sand epoch, at least so far as our knowledge 

 of the cardinal character of simulating forms extends. The 

 hino-es of the species figured by Pictet and Roux, from the " Gres 

 Vert " near Geneva, are not figured or described, and therefore 

 the shells are but conjectural members of Astarte. 



^rvji> ^-^^5 y ^''-■''' -^ ASTARTE, Sowerby. 



Hinge character. Cardinal plate broad ; cardinal teeth two in 

 each valve ; anterior cardinal margin raised into a distinct lateral 

 tooth as long as the lunule in the right valve, which fits into a 

 corresponding furrow on the opposite valve ; posterior lateral 

 tooth or elevated margin in the right valve elongated ; furrow in 

 the opposite valve broad, resembling that of Unio. 



A. LURIDA, Sowerby. — PI. 9, fig. 2. 

 A ELEGANS, Sowerby. — PI. 9, fig. 13. 



In the Chalk period and its equivalents no hinge has been de- 

 scribed or figured answering to the typical Asitarte, but there 

 are intermediate forms between Crassatella and Astarte which 

 make a complete chain of genera in the family. , -,, j 



LIRODISCUS, Conrad, ^^w^.' >'«jl^^'W; '^ Jii^<.yy^- 

 Equivalve; disk concentrically ribbed ; posterior side lobed by "^'^^'^ 

 an impressed line; hinge with two cardinal teeth in each valve; 

 right valve with a small pyramidal lateral tooth near the an- 

 terior cicatrix ; left valve with the same posteriorly and distant 



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