199 



lucidd, concentrice sulcatd ; latere postico longiore, subacuminato, 

 untico brevissimo : long. 0"2, lot. O'l, alt. 0'15 poll. 

 Hab. ad Columbiam Occidentalem (Bay of Caraccas). 

 A single specimen found in sandy mud at nine fathoms depth. — 

 G. B.S. 



Genus Amphidesma. 



Amphidesma roseum. Amph. tesid suborhiculari, rosed, concen- 

 tricf costatd, epider mid e fused, lucidd, indutd ; latere postico sub- 

 emarginuto ; costis confertis, acutis : long. 2-5, alt. 2-3, lat. 1"1 

 poll. 

 Hab. ad littora Peruvise. 



Shell of a rose colour all over ; darker about the umbo. A single 

 valve was found at Tumbez in Peru. — G. B. S. 



Amphidesma Rupium. Amph. testd subovali vet suborbiculari, sub- 

 irregulari, radiatim striatd, costis interruptis concentrice rugosd ; 

 umbone Icevigato ; intiis albd; dentibus later alibus subapproximatis, 

 hrevibus, crassis,7narginequedorsali posticd purpureis: long. 1 25, 

 alt. I, lat. 0-65 poll. ; long. IS, alt. \-2, lat. 0*7 poll. 

 Hab. in Oceano Pacifico. 



Outside of the shell white ; a few rose-coloured rays are occasion- 

 ally observable near the basal margin. Found in coarse gravel in 

 the crevices of rocks in coral reefs at Lord Hood's Island. A variety 

 which is white all over, both inside and out, occurs in the clefts of 

 rocks in coarse gravel at the Gallapagos Islands. — G. B. S. 



Amphidesma formosum, Amph. testd ovali, alhicante, rosea 

 radiatd et piirpureo maculatd, concentrice costatd, costis confertis, 

 antice posticeque rugidosis ; nmbonibus intfis lutescentibiis : long. 

 2, alt. 1-6, lat. 0-7 pell. 



Hab. ad Sanctam Elenam, 



The most beautiful of all the Amphidesmata I have yet seen. Only 

 two odd valves were dredged in seven fathoms water. — G. B. S. 



Amphidesma pallidum. Amph. testd ovali, pallide purpurascenti- 

 fulvd, umbonibus saturatioribus, tenuissime concentric^ striatd, epi- 

 dermide tenui, subiridescente indutd ; latere postico subtruncato, 

 dorsali rotundato : long. 1-25, lat. 0*45, alt. 0*9 poll. 



Hab. ad Salango, Columbia Occidentalis. 



The young shells are paler and more fulvous in colour. Dredged 

 in sandy mud at a depth of seven fathoms. — G. B. S. 



Amphidesma l.eve. Amph. testd ovatd, albd, Icevigatd, epider7nide 

 corned, tenui indutd; latere postico breviore, rotundato, antico 

 longiore subacuminato ; sulco obsoleto posticali, ab timbone ad 

 marginem ventralem decurrente : long. 145, alt. I- 1, lat. 035 

 poll. 



Hab. ad Xipixapi, Columbiae Occidentalis. ■ 



A single specimen of this very delicate species was dredged from a 

 depth of ten fathoms in sandy mud. — G. B. S. 



Amphidesma purpurascens. Amph. testd ovali, purpurascente ; 

 mar gine untied rotundatd , posticd subacuminatd, subtruncatd, dor- 



