199 



luciddy concentrice sulcata ; latere portico long tore, subacuminato, 

 antico brevissimo : long. 0*2, lat, 0*1, alt.Q'\5 poll. 

 Hob. 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. testd suborbiculari, rosed, concen- 

 trice costatd, epidermide fused, lucidd, indutd ; latere postico sub- 

 emarginato-, costis confertis f acutis : long. 2*5, alt. 23, lat. 1*1 

 poll. 

 Hub. ad littora Peruvian. 



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

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



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

 irregulari, radiatim striatd, costis interrvptis concentrice rv.gosd ; 

 umbone laevigata ; intiis albd; dentibus lateralibus subapproximatis, 

 brevibus, crassis, mar ginequedorsali posticd purpureis : long. 125, 

 alt. I, lat. 0-65 poll. ; long. 1-3, alt. \% lat. 0-7 poll. 

 Hab. in Oceano Pacifico. 



Outside of the shell white j 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, albicante, roseo 

 radiatd et purpurea maculatd, concentrice costatd, costis confertis, 

 antice posticeque rugulosis ; umbonibus intiis lutescentibus : long. 

 2, alt. \'6, lat. 0-7 poll 



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 concentrice striatd, epi- 

 dermide tenui, subiridescente indutd ; latere postico subtruncato, 

 dorsali rotundato : long. 125, 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, epidermide 

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

 longiore subacuminato ; sulco obsoleto posticali, ab umbone ad 

 viarginem veniralem decurrente: long. 145, alt. 11, lat. 35 

 poll. 



Hab. ad Xipixapi, Columbia? 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 ; 

 margine untied rotundatd, posticd subacuminatd, subtruncatd, dor- 



