30~ HELICIDiE. 



and impressed sutures ; last whorl narrow, not descending in 

 front; aperture slightly oblique, rounded-lunate; peristome 

 simple, acute, margins joined. H. dissimilis, Orb. South 

 America. 



Macrocycloides, Martens, 1861. Shell depressed, almost 

 planorboid, shining, striate, hj;- aline, base slightly excavated, 

 showing all the whorls ; peristome acute, the margins slightly 

 approaching. H. ohscurala, Ad. and RecA^e. 3 sp. East Indies. 



P%s, Beck, 1837. (Endodonta, Albers, 1850.) Shell small 

 or minute, corneous, frequently with longitudinal brown bands, 

 umbilicated or rarely subperforated ; conical, orbicular, depressed 

 or discoidal ; aperture lunar, angular, very rarely rounded, with 

 lamellar teeth upon the interior or* parietal walls, or both ; peris- 

 tome simple, sharp. 56 sp. Polynesia. H. lamellosa, Fer. 

 H. contorta, Fer. (xciv, 11). Sandwich Islands. 



Libera^ Garrett, 1881. Shell small, widely umbilicated, umbil- 

 icus (in adults) strongly constricted, so as to form a cavernous 

 or pouch-like cavity ; whorls 7-9, costulate or striate, last one 

 angulate or carinate, rarely rounded ; peristome simple; parietal 

 region with one or two, and the palate with two or three internal 

 laminae ; columella emarginate and furnished with a spiral fold. 

 Polynesia. H.fratercula^'Pea.se. Remarkable for their singular 

 habit of ovipositing into their cavernous umbilicus — the con- 

 striction of which does not occur until the last two whorls are 

 completed. Sometimes a temporary shell}^ plate retains the eggs 

 or young within the umbilicus. 



Laoma, Gri'^y, 1849. Shell turreted, conical, scarcely per- 

 forated, smooth , pellucid, shining ; whorls seven, flattened, the last 

 carinated, base plane; aperture square depressed, lamellate ; lip 

 simple. H. leivionias, Gray. 2 sp. 



Gharopa, Albers, 1860. Shell thin, depressed, rarelj^ conical, 

 umbilicated, with transverse ribs, sparsely bristly; whorls 4-5|-, 

 the last not deflected in front ; aperture slightly oblique, lunately 

 rounded ; peristome simple, margins joined. H. coma^ Gray 

 (xciv, 12); New Zealand. 48 sp. ; Australasia. 



Trocliomorpha^ Albers, 1850. (Geotrochus, Van Hasselt.) 

 Shell umbilicated or subperforated, trochiform, the apex more 

 or less obtuse ; whorls somewhat flattened, the last with a 

 carinated periphery ; aperture depressed, oblique ; peristome 

 simple ; columellar lip rarely thickened or dentate. 165 sp. 

 India, East Indies, Polynesia. 



Nigritella, Albers, 1860. Depressed trochiform, umbilicated, 

 striate, shining, dark brown or blackish ; whorls 7-8, the last 

 plane or excavated beneath ; aperture depressed, oblique, semi- 

 oval or elliptical; peristome simple, thickened, outer margin 

 flexuous, columellar margin callous. H. nigritella^ Fer. H. 

 Pagodula, Pfr. (xciii, 4). 



