TERRESTRIAL MOLLUSCA INHABITING SOCIETY ISLANDS. 
93 
Tliey are distributed over a vast area extending from soxxtheastern Polynesia to 
Mauritius and Bourbon. They are entirely absent from the Sandwich Islands, where 
the only operculated land shells are Helicinoe. Two species of Atroins only are recorded 
from the Marquesas Islands ; but their existence in that group certainly wants confir- 
mation. Both Mr. Pease’s collector and myself searched in nearly all parts of the 
group without discovering a single example. In all probability the Society Islands 
are the eastern limits of this group of shells. At any rate I utterly failed to detect 
them at the Gambler and Paumotu Islands. 
In the Society Islands the typical form is represented by a group in which the keel 
gradually becomes evanescent, as in Huahemensis and scitula, or entirely absent, as in 
terebralis and producta. The three latter were classed by Mr. Pease in his genus 
Atropis. All the above species, together with Borahorensis and oblonga, usually 
have the body or penultimate u horl more or less angulated and frequently with a 
periphery keel. 
The animal of HvaJieinemis varies from pale cinereous to tawny flesh-color with 
blackish tentacles, which latter are short, conical, blunt and transversely wrinkled. 
Eyes very conspicuous, black on enlargements at the hinder base of the tentacles. 
Head broad, emarginate in front. Muzzle slightly dilated and bilobed in front, and 
used in aiding locomotion. Foot small, oval, nearly half the length of the shell. 
0. Huaheinknsis, Pfeiffer. 
Hydrocena Iluaheinensis, Pfeiffer, Proc. Zool. Soc., 1854, p. 308; Mon. Pneum., ii, p. 163. 
11. and A. Adams, Gen. Moll., ii, p. 300. 
Omphalotropis Huaheinensis, Pfeiffer, Mon. Pneum., iii, p. Iff. Mart, and Langk., Don. 
Bism., p. 58, PL III, fig. H. Pease, Jour, de Conch., 1869, p. 148, PI. VII, fig. 9. 
Schmeltz, Cat. Mus. Godeff., v. p. 101. Pease, Proc. Zool. Soc., 1871, p. 476. 
Assiminea Huaheinensis ^ Marten, Ann. Mag. Nat. Hist., 1866, p. 206. 
. Realia Huaheinensis, Pfeiffer, Mon. Pneum., iv, p. 221. Carpenter, Proc. Zool. Soc., 1871, 
p. ()76. 
Hydrocena robusla, “ Pease,” MS. Carpenter, Proc. Zool. Soc., 1864, p. 676. 
Omphalotropis robusta, Crosse, Jour, de Conch., 1869, p. 148 (foot-note), PI. VII, fig. 3. 
Schmeltz, Cat. Mus. Godeff., v, p. 208. 
Occurs in abundance, and widely diffused over Huaheine. It is also plentiful 
and of larger size in three or four valleys on the west side of Raiatea. At Moorea, 
where I obtained a few examples, it is of small size (5 mill.) and has the basal keel 
nearly or quite obsolete. On the groxind in forests. 
Pfeiffer’s type specimens (9 mill.) were collected at Raiatea, and his var. /9(6 mill.) 
at Htiaheine. In one valley on the former island I discovered a large variety which 
attained a length of 1 1 mill. i, • i j 
They vary considerably in color: pale luteous, corneous, broxvn, brownish red, 
reddish horn-color, rarely with a transverse brown or reddish band on the middle of 
the body-whorl, which latter is sometimes sUghtly angulated. The epidermis is very 
13 JOUR. A. N. s. PHILA., VOL. IX. 
