48 



The two muscular impressions are situated on each side of the in- 

 terior a little below the summit ; vvhile, in Patella, they nearly 

 sunound the internal circumfeience of the šame part of the shell. 

 The aperture is generally surrounded by a margin, and the apex, 

 which in Ancylus is oblique, is centrai though posterior. 



Mr. Cuming biought home the foliovving species vvhich I now pro- 

 ceed to desciibe. 



ScuTELLA CRENULATA. Scut. testd subcoTiicd, concellatd, striis ah 

 apice radiantibus exasperatis, albd ; intūs nitente ; annulo niar- 

 ginali et margine crenulatis : long, %, lai. ^, alt. -rV poli. 



Hab. ad insulam Anaan (Chain Island). 



This shell was found dead on coral sand on the beach of the island 

 at a distance from any fresh water. 



The marginai ring is very strongly developed, and the margin it- 

 self is not even ; for vvhen the shell is placed with the aperture down- 

 wards on a flat surface, it rests on the two ends» the sides of the 

 margin forming each a low arch. 



ScuTELLA iRiuESCENS. Scut. testd oblotigo-ovatd, complaiiatd, mi- 

 nutissme substriatd, albo et roseo guttatim tessellatd ; intūs iri- 

 descente, margine interno albo, roseo maculato : long. -rS, lat. iV* 

 alt. tV poli. 



Hab. in Oceano Pacifico. (Grimwood's Island.) 



This species was gathered by Mr, Cuming on the sands when the 

 tide was out. There vvas no fresh water near, and though he obtained 

 Severai individuals in the finest condiiion, the soft parts were gone, 

 having evidently but lately fallen a prey to some carnivorous crea- 

 ture. 



The shape of Scut. iridescens is very elegant, and the silvery iri- 

 descent nacre vvhich lines the inside of the shell, contrastedas it is 

 with the less briiliant but lively coloured margin, is almost dazzling. 

 The back of the shell, which is very brittle, is mottled with white and 

 rose colour. This disposition of its markings almost conveys the ira- 

 pression that the surface of the back is uneven ; but with the excep- 

 tion of the very minute stria, vvhich are almost imperceptible, it is 

 smooth. 



ScuTELLA ROSEA. Scut. iesld' subcoTiicd , striatd, albd, lineisjlam' 

 mulisgue roseis ornatd; intiis niteute, inlerduni subiridescente : 

 long. -į", lat. ^v> olt- TT- poli. 



Obs. Varietas forsan preecedentis. 



Hab. cum praecedente. 



The shape and many other points in this shell differ from those of 

 Scut. iridescens. Externally it is much more conical and the stria 

 vvhich run from the apex to the interior margin aredirect and minute, 

 while those vvhich are lateral are much coarser and cross the some- 

 what elevated white parts obliquely : in Seat. iridescens, the exceed- 

 ingly minute strice radiate evenly from the apex. In Scut. rosea we 

 lose the brilliancy of the internal nacre vvhich distinguishes Scut. 

 iridescens, and^ in some individuals, it is entirely absent. Still the 



