stone. The attached valves have not attalned a great degree of 

 thickness, conseąuently I do not suppose any one of the individuals 

 to be of advanced age ; there are, liowever, several which can only 

 just have occupied their positions on the stone : these are not above 

 tV part of an inch in diameter, and they show the perfect point of 

 the upper valve, somewhat convoluted and inclined toward the ante- 

 rior edge. Other individuals, which are placed in a cavity of the 

 stone, are very regular in shape, but have their ridges slightlj' curved 

 upAvards in eonformity with the nearly regular vesicular shape of the 

 cavity. The edges of the lamellts near the outer margin in most of 

 the specimens are furnished with a thin fringe of epidermis, but the 

 very young shells are destitute of this. An individual of Hipp. 

 ^siibnifa is observable among the group of Hipp. Mitrula: its ape.v is 

 distinctly spirai and its epidermis hairy. 



' ' The second specimen belongs to the species which I have named 

 Hipp. burhata. This is a very complete specimen, and reminds me 

 of the beautiful fossil species Hipp. Cornucopice ; it is a small indivi- 

 dual, having its attached valve very much thickened and adhering to 

 a much larger one of the šame species ; its edge is much elevated 

 and it is deeply concave ; the free valve is rather smaller, and coni- 

 cal, and its edge is surrounded by the elevated edge of the attached 

 valve."-G. B. S. 



HippoNYx Mitrula. (Pileopsis Mitrula, Lam. PateUa Mitrula, 

 Auct.) Hipp. testd albd, suhconicd, concentrice lamellosd, la- 

 mellis subconfertis, radiatim striatis, epidermide pilosis. 



Hab. ad Insulam Peruvianam Lobos dictam. 



Found upon stones, in seventeen fathoms' -ffater, among coarse 

 sand.— G. B. S. 



HiPPOxYX suBRUFA. (Pilcopsis subrufus, Lam. Patella subrufa, 

 Dilltv.) Hipp. testd aurantiaco-rufescente, subconicd, concen- 

 trice sulcatd, radiatim striatd, striis profundis, marginibus sulco- 

 rum crenulatis ; vertice postice incUnato. 



Hab. cum prsecedente. — G. B. S. 



HippoNYx KADiATA, Gray. Hipp. testd subdepresso-conicd, ful- 

 vescente, radiatim costatd, costis crebris, imbricato-sguamosis ; 

 vertice postico. 

 Hab. ad Panamam et ad Insulas Gallapagos. 

 Found attached to rocks alive, and the upper valves loose on the 

 sands.— G. B. S. 



HiPPONyx BARBATA. Hipp. tcstd pūlUde fulvd, subelevato-conicd, 

 radiatim confertim striatd ; margine ventrali pradučio ; epider- 

 mide piloso-barbatd ; margine interno crenulato. 



Hab. ad Insulas Maris Pacifici. 



Found on the coral reefs around Toobouai, one of the Society 

 Islands.— G. B. S. 



