CUMINGIA. 



I'ESTA bivalvis, insequilateralis, aequivalvis, 

 latere antieo rotimdato, postieo siibaeuminato; 

 dentibus, cardinal! in iitraque valva unieo, 

 parvo, antieo; lateralibus in altera valva ad 

 iitrunique latus uno, valido, in altera nullo: 

 ligamento interne foveolae subcochleari- 

 formi affixo; impressionibus muscularibus dua- 

 bus, lateralibus, distantibus, antica irregular], 

 oblonga, postica subrotundata, impressione 

 musculari pallii sinu maximo. 



C3 



An interesting new Genus of bivalves which should be 

 placed near to Amphidesnia. It is remarkable for the 

 dissimilarity of the hinge of the two valves, one having a 

 strong laterfil tooth on each side of the ligament and the 

 other being entirely destitute of lateral teeth. Having 

 only met with a single small West Indian species we could 

 not venture to consider this Genus as established, until Mr. 

 Cuming showed us several species in his rich collection of 

 South American and Pacific shells, one of which is 

 sufficiently large to show the characters distinctly. 



The Cumingia are inequilateral, equivalve bivalves, 

 with the anterior side rounded and the posterior rather 

 acuminated. A single small anterior cardinal tooth is 

 observable in each valve: and there is one strong lateral 

 tooth on each side of the hinge in one valve, but no late- 

 ral tooth in the other valve ; the ligament is internal and 

 affixed to a somewhat spoon-shaped pit in each valve. The 

 muscular impressions are two in each valve, they arc 

 lateral and distant, that which is anterior is irregular and 

 oblong 5 the posterior is rounded. There is a very large 

 sinus in the muscular impression of the mantle. 



The shells of this Genus are marine, they are found 

 in the sand in the fissures of rocks, and as far as we yet 

 know they are tropical. Not known in a fossil state. 



