137 



Genus 1. CUMIN GI A, Sowerby. 



Animal ; unknown. 



Shell ; equivahe, inequilateral, anterior side rounded, posterior 

 more or less acuminated and a little gaping ; hinge composed of 

 a small anterior tooth in each valve, with two strong lateral 

 teeth in one valve only, the ligament being within an inioardly 

 projecting spoon-shaped cavity. 



At the head of the Mactracea we have a genus of which the shell is 

 found in sponges and in fissures of rocks, like the shells of the preceding 

 family, but of which the hinge-ligament is contained within an inwardly 

 projecting spoon-shaped cavity. It was founded in 1833 on some speci- 

 mens collected by Mr. Cuming on the western coast of South America, 

 presenting, in addition to these characters, the somewhat anomalous one of 

 having two well-developed lateral teeth in one valve and none in the other. 

 Four species were defined on its discovery by Mr. Sowerby ; six, from the 

 same locality and the West Indies, were described seventeen years later by 

 Mr. Arthur Adams ; and D'Orbigny and Conrad described four species. 

 They are rather slight and colourless, mostly rudely lamellated, and all of 

 them gape a little posteriorly. They seem to be allied to Amphidesma, 

 but their place in the system cannot be satisfactorily determined until the 

 animal is known. 



1. Antillarum, D'Orb. 



2. Califomica, Conr. 



3. Clerii, Adams. 



4. coarctata, Sow. 



5. fragilis, Adams. 



Species. 



6. lamellosa, Sow. 



7. rnutica, Sow. 



8. Petitiana, D'Orb. 



9. similis, Adams. 

 10. sinuosa, id. 



11. striata, Adams. 



12. Tellinoides, Conr. 



13. tenuis, Adams. 



14. trigonularis, Soto. 



Figure. 



Cumingia mtjtica. PI. 39. Fig. 213. Shell, with one valve dropped to 

 show the inwardly projecting spoon- shaped cavity containing the 

 ligament. 



VOL. II. 



