New Species of Corhula from Jamaica. 285 



or quite rectilinear; posteriorly and inferiorly acuminate: 

 white : with large blunt edged concentric ribs, which are more 

 slender in the posterior area ; with microscopic radiating lines 

 of deciduous tubercles, which are visible only under a good 

 magnifier ; with both valves sculptured alike : beaks prominent, 

 slightly involute: umbones flattened, with a stout posterior 

 angle : teeth rather small. Under a good magnifier a crystalline 

 structure is very conspicuous. 



Length .44 inch ; height .26 inch ; breadth .18 inch. 



Station. — Muddy bottom, at the depth of 8 or 4 fathoms ; C. 

 B. A.! 



Habitat. — Port Eoyal, in Jamaica; C. B. A. ! 5 specimens 

 were collected. 



CoRBULA DiETZlANA. C. t. solida, vald^ distortu, juniore 

 vix inequivalvi, seniore perinequivalvi, inequilaterali ; margine 

 antice rotundata, aliunde rectilineari, postic^ infra acuminata: 

 albida, radiis rubris, inequalibus, s^epe confluentibus, in juniore 

 obsoletis, ornata: costis magnis, subacutis, concentricis, in 

 seniore irregularibus et in valva parva exilibus : apicibus pro- 

 minulis, vix involutis: umbonibus planulatis, posticfe valde 

 angulatis : dentibus robustis. Long. 10"'.7 ; alt. 8"'.4 ; lat. 9"'.l : 

 junioris, long. 10"'.l ; alt. 6"'.6 ; lat, 4"'.3. 



Shell solid, much distorted, moderately inequivalve in the 

 first stage of growth, afterwards very inequivalve, inequilateral ; 

 anteriorly well rounded, with the other margins subrectilinear, 

 posteriorly and inferiorly acuminate: whitish, with unequal 

 often confluent bright red rays, which are indistinct in the first 

 stage of growth : with concentric blunt edged unequal ribs, 

 which are more irregular in the last stage of growth ; with both 

 valves sculptured alike in the first stage of growth, but in the 

 second, the small valve is only striated: beaks prominent, 

 sHghtly involute: umbones flattened, with a strong posterior 

 angle : teeth rather stout. 



Length .42 inch ; height .33 inch ; breadth .36, The corrc- 



