26 TERRESTRIAL MOLLUSCA INHABITING SOCIETY ISLANDS. 
says inhabits Tahiti and Samoa; the latter location is undoubtedly wrong. Mr. Pease 
says (Jour. de Conch., 1870, p. 399) Cressida is a good species, and inhabits Raiatea. 
Having personally collected all Mr. Pease’s Raiatea shells, and having now before me 
numerous duplicates, I have failed to discover one which coincides with Gould’s 
description, Mr. Pease’s Helix lenta, MS. (= Sirainsoni, var.), is the nearest allied 
form, but is much smaller, thinner and has a more convex base. 
Dr. Gould’s original description is as follows :— 
“'T. variabilis, solida, depressa, lenticularis, acute carinata, nitida, dense et acute 
striata, coloribus flavo-viridibus et castaneis coalescentibus fasciata, infra subplanulata, 
umbilico magno et profundo perforata; anfr. 5 vix convexi; apertura triangularis ; 
labrum acutum ; faux lilacina.—Lat. 7%, alt. } poll.” (Gould). 
The only shell I can satisfactorily refer to the above diagnosis is a somewhat scarce 
species inhabiting two large valleys on the northwest side of Tahiti. The localities 
are near the two principal harbors and probably were the first ones explored by the 
naturalists of Wilkes’ Expedition. 
I have now before me five examples, the largest measuring 18 mill. in the major 
diameter and 6 in height. It is a solid, shining, depressed shell, with crowded, 
irregular, rather sharp, obliquely curved strive, and 5-54 subplanulate whorls. The 
suture is margined by the continuation of the acute periphery-keel. The flatly convex 
base exhibits a wide umbilicus in which may be easily enumerated all the volutions. 
The color is light yellowish brown, with or without a dorsal and basal light chestnut 
band which gradually fades mto the ground color, Occasionally the basal band is 
obsolete, and the dorsal one so faint as not to be seen except in certain lights. The 
aperture is diagonal, depressed, securiform, with three angles which suggested Gould’s 
“apertura triangularis.” The peristome, above the carination, is trenchant, rectilinear 
and regularly curved from the keel to the columellar region, the inner margin 
strengthened with callus. 
T. Swarnsont, Pfeiffer. 
Helix Swainsoni, Pfeiffer, Proc. Zool. Soc., 1846, p. 28; Mon. Hel., i, p. 122; (Videna) 
Vers., p. 132. Reeve, Conch. Icon., fig. 607. Carpenter, Proc. Zool. Soc., 1864, p. 675. 
Schmeltz, Cat. Mus. Godeff., v, p. 95. 
Zonites Swainsoni (Rotula), H. and A. Adams, Gen. Moll., ii, p. i116. 
Helix scuta, Pease, MS. Coll. Pease, 1863. 
Helix lenta, Pease, MS. Coll. Pease, 1863. 
Nanina Swainsoni (Rotula), Paetel, Cat. Conch., p. 85. 
Trochomorpha Swainsoni, Pease, Proc. Zool. Soc., 1871, p. 474 (part). 
This species, which inhabits Raiatea and Tahaa, occurs in nearly all the large 
valleys, but is not nearly so plentiful as ¢rochiformis. It is a ground species, and 
may be found lurking under rotten logs, among decaying leaves, and, during rainy 
weather, may be seen creeping a short distance up the trunks of trees. 
