TERRESTRIAL MOLLUSCA INHABITING SOCIETY ISLANDS. 
39 
late walls. In adults there are eight flat whorls, the last three subcoucave, and tlie 
aperture is a nearly equally four-sided square. 
Var. PiCEA, Garrett. 
This variety, Avhich I have distributed to my correspondents under the name of 
Pitys picea, differs none from the type, except in being smaller and the parietal wall 
unilaminate. The aperture is also vertically narrower. 
Not infrequent on the west side of Eaiatea. 
E. OBOLTJS, Gould. 
Helix obolus, Gould, Proc. Bost. Soc. Nat. Hist., 1846, p. 115 ; Expl. Ex. Shells, p. 53, fig. 50. 
Pfeiffer, Mon. Hel., i, p. 187. 
Endodonta obolus, Albers, Die Hel., ed. 2d, p. 90. Pease, Proc. Zool. Soc., 187 1 , p. 474. 
Pitys obolus, H. and A. Adams, Gen. Moll., ii, p. 114. 
Patula obolus, Schmeltz, Cat. Mus. Godeff., iv, p. 72. Paetel, Cat. Conch., p. 93. 
Helix acetabulum, Pease, Proc. Zool. Soc., 1861, p. 242. Pfeiffer, Mon. Hel., v, p. 222. 
Endodonta acetabulum, Pease, Proc. Zool. Soc., 1871, p. 474. 
Pithys? celsa, Pease, Jour, de Conch., 1870, p. 396. 
Endodonta celsa, Pease, Proc. Zool. Soc., 1871, pp. 455, 474. 
Helix celsa, Pfeiffer, Mon. Hel., vii, p. 260. 
Patula Barffi, Garrett, Schmeltz, Cat. Mus. Godeffr., v, p. 93. 
Patula intermixta, “ Mousson,” Schmeltz, Cat. Mus. Godeff., v, p. 93. 
This variable species, which is confined to Eaiatea and Iluaheine, is plentiful and 
widely diffused over the two islands. 
Dr. Gould’s habitat, “ Taheiti,” is undoubtedly wrong. Having personally explored 
every valley on Tahiti and Moorea, I did not find a single example of this tyi>c of 
Helices. His specimens were probably from Eaiatea. Dr. Gould describes it as 
follows: — . 
“ T. parva, discoidea, deorsum compressa, supra planulata, infra concava, radiatim 
minutissima et iuEequaliter striata, fusco-ferruginea, piceo tessellata ; spira; anfr. 5^, 
supra excavati, ultimus superne costato-carinatus ; apertura subrhomboidea, faucc 
lamella unica semmdum anfractum penultimum volventi. Lat. i, alt. poU- 
(Gould). . 
The above description accords well with the shells under consideration, and tlie 
“supra excavata” agrees better with the Eaiatea shells than those from Iluaheine. 
But the above author’s reference to Planorhis vortex as similar in shape renders tlie 
identification beyond doubt. 
I am fully convmced that Pease’s acetabulum is specificaUy the same as Gould s 
species. 
Mr. Pease’s diagnosis, which is rather obscure, I reproduce ; 
••T. par™, planorboidea, superne leviter convexa vel plana; umb.licus ainplus, 
cyathiformis; utriuque subtililer radiato-striata, ad periphcriam et umbilici iiiargiucm 
