GASTEROPODA. A5 
is suddenly twisted inwards, forming a narrow channel, nearly con- 
cealed, just under the penultimate whorl. 
Diameter one-fourth of an inch; axis one-sixth of an inch. 
Inhabits the mountains of Oahu, Sandwich Islands. 
This shell belongs to a group in which the specific marks are very 
faintly pronounced. It has a general resemblance to H. cicercula, but 
is somewhat larger, clearer, less globose, and by a careful examination 
of the aperture, a peculiar channel at the top of the columella, almost 
microscopic, indeed, will leave no doubt. ‘The umbilical region is 
also more striated. To H. cultrata it is also closely allied. It still 
more nearly resembles H. subrutila ; but that shell has microscopic 
revolving lines, is more depressed and somewhat sharply angular at 
periphery, has not quite five whorls, and the columella joins the 
whorl above without the intortion which forms the little umbilical 
channel of this shell. It is smaller and less pyramidal than H. 
Tongana. 
Figures 72, 72a, 726, three views of the shell, enlarged; 72, 
natural size. 
HELIX PERTENUIS (Gould). 
Testa minuta, subglobosa, pellucida, nitidissima, viridi-aurea, imperfo- 
rata : spira depressa, anfractibus quatuor cum dimidio, convexis, ultimo 
amplo, ad peripheriam angulato, infra sulcis remotis radiato: aper- 
tura ampla, lunata ; labro simplict. 
Helix pertenuis, Goutp; Proceed. Boston Soc. Nat. Hist., i. 172. 
Sept. 1846. Expedition Shells, 172. Prerirrer; Monog. Helic., i. 38. 
SHELL small, pellucid, subglobose, depressed above, more convex 
and imperforate beneath, of a gilded green colour, very minutely 
striated, and divided into segments by gooseberry-green radiating 
lines. Spire depressed, whorls four and a half, convex, the outer 
one large, and obtusely angular at the periphery; suture well defined. 
Aperture ample, rounded-lunate ; lip simple. 
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