199 



lucidd, concentrice sukatd ; latere postico longiore, subacumitiato, 

 anlico brevissimo : long. 0'2, lat. 0*1, alt. 015 poli. 

 Ilab. ad Coluiubiam Occidentalem (Bay of Caraccas). 

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

 G. B. S. 



Genus Amphidesma. 



Amphidesma roseum. Amph. testd suborbiciilari, rosed, concen- 

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

 emarginato ; costis confertis, aaitis : loug. 2'5, alt. 2-3, lat. l'l 

 poli. 

 Hab. ad littora Peruviae. 



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. testu subovali vel suborbiculari, sub- 

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

 umbone Icevigato ; intus albd; dentibus lateralibus subapproiiniatis, 

 brevibus, crassis, marginequedor sali posticd purpur eis : loiig. \2b, 

 alt.\, lat. 0-65 polL; long. 1-3, alt. \2, lat. 07 poli. 

 Hab. in Oceano Pacifico. 



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

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

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

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

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



Amphidesjia formosum. Amph. testd ovali, albicante, roseo 

 radiatd et purpureo maculatd, concentrice costatd, costis confertis, 

 antice posticeqne rugulosis ; umbonibus intus lutescentibus : long. 

 2, alt. \-6, lat. 0-7 poli. 



Hab. ad Sanctam Elenam. 



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

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



Amphidesma pallidum. Amph. testd ovali, pallide purpurascenti- 

 fulvd, umbonibus saturatioribus, tenuissime concaitrici striatd, epi- 

 dermide tenui, subiridescente indutd; latere postico subtruncato, 

 dorsali rotundato : long. 125, lat. 0-45, alt. 0'9 poli. 



Hab. ad Salango, Columbiae 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 ova ta, albd, Icevigatd , epidermide 

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

 longiore subacuminato ; sulco obsoleto posticali, ab umbone ad 

 viargineni ventraleni decurrente : long. 1-45, alt. l[, lat. O 35 

 poli. 



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. lesta ovali, purpurascente ; 

 margine anticd rolundatd, posticd subacuminald , subtruncatd, dor- 



