THE ANNALS 



AND 



MAGAZINE OF NATURAL HISTORY. 



SUPPLEMENT TO VOL. VIIL MARCH 1842. 



LVL — On a new genus of Fossil Bivalve Shells. By Mr. 

 Samuel Stutchbury, F.G.S., A.L.S., &c., Curator of 

 the Bristol Institution. >: 



[With two Plates.] 



Some years since my attention was called to several species 

 of bivalve shells which were generally placed in the genus 

 Unio ; upon a close examination of many specimens, I was 

 enabled to characterize eight or nine species certainly distinct 

 from any established genus ; also finding that they appeared 

 to be confined to the lias and inferior oolite, which are deter- 

 minate marine beds, I was anxious to remove them from the 

 genus Unio, with which they appeared to have but slight ana- 



With this view I forwarded, in 18.37^ a paper to the then 

 editor of the ' Magazine of Natural History,^ which from some 

 cause was not inserted ; but in the meantime the name Pa- 

 chyodon, by which I had designated the new genus, became 

 pretty generally adopted b}^ those who had access to the Mu- 

 seum of the Bristol Institution. I have since been informed 

 that Professor Agassiz has given, or intends to notice the 

 genus under the name of Cardinea : if he has already done so, 

 I shall yield the name Pachyodon, being anxious not to in- 

 crease the ah'eady overloaded list of synonyms. 



In the list of genera published in the ' Synopsis of the Bri- 

 tish Museum,' by J. E. Gray, Esq., it is designated by the 

 name of Ginorya, and arranged among the Crassinidce, but no 

 description accompanies the name. 



I have also to observe, that both in the ' ^lineral Concho- 

 logy ' and in the ' Genera of Recent and Fossil Shells,' the 

 Messrs. Sowerby, with their accustomed acumen, had thrown 

 considerable doubt upon the propriety of continuing these 

 several species in the genus Unio. 



PACHYODON. 



Gen. Char. — Shell bivalve, equivalve, inequilateral; hinge con- 

 sisting of a single, oblique, thickened cardinal tooth in the right 

 valve, with a hollow for its reception in the left valve ; anterior la- 

 teral tooth in the right valve obtusely conical ; the posterior lateral 



Ann. 6f Mag. N. Hist. Vol. viii. Suppl. 2 I 



