GASTEROPODA. 63 
This bears a general resemblance to H. pyramidata ; but with the 
same diameter, it is less elevated, and more rounded at apex. 
Figures 53, 53 a, 53}, three views of the shell. 
HELIX TENTORIOLUM (Gould). 
Testa parva, elevata, trochiformis, ad apicem rotundata, pallid? vires- 
cens, obliqué et concinne striata, bast in umbilicum mediocrem devexa : 
spira anfractibus sex planulatts, et carina acutissima, alba, cinctis : 
apertura subtriangularis, bast rotundata ; labro simplict, ante umbil- 
cum reflexo. 
Heliz tentoriolum, Goud; Proceed. Boston Soc. Nat. Hist., ii. 176. 
Sept. 1846. Expedition Shells, 23. Prrirrer; Monog. Helic., i. 119. 
ANIMAL greenish, dark violaceous on the neck, with a dark line 
running back from each tentacle; there is a bluish line along the 
flanks, and a yellowish-green margin with radiating marginal linea- 
tions. Surface finely reticulated. 
SHELL small, delicate, trochoid, height and breadth about equal, 
apex obtusely rounded, delicately striated by the lines of growth, of a 
pale or sap-green colour. Whorls six, nearly plane, the periphery of 
each having a sharp, elevated, whitish carina, which overhangs the 
suture of the last three whorls, and very distinctly marks the limit of 
each one. The base is gently swelling, midway between the margin 
and umbilicus, which is of moderate size, with a regularly rounded 
entrance. Aperture sub-triangular, the basal portion rounded; lip 
simple, columellar portion nearly vertical, and slightly reflected about 
the umbilicus. 
Diameter two-fifths of an inch; axis three-tenths of an inch. 
Inhabits Upolu, Samoa Islands. Couthouy. 
Its elevated form and rounded summit, resembling a nipple, is very 
remarkable. 
Figure 54, the animal with the shell. 
