64 TERRESTRIAL MOLLUSCA INHABITING SOCIETY ISLANDS. 
P. rivosa, Pfeiffer. Plate ITI, fig. 81. 
Partula filosa, Pfeiffer, Proc. Zool. Soc., 1851, p. 262; Mon. Hel., iii, p. 450. Chemnitz, 
ed. 2d, Bul., p. 267, Pl. LXIV, figs. 3,4. (Helena) Hartman, Cat. Part., p.10; Obs. 
Gen. Part., Bul. Mus. Com. Zool., ix, pp. 182, 183, 196. 
Partula lineolata, Pease, Amer. Jour. Conch., 1867, p. 224; Proc. Zool. Soc., 1871, p. 473. 
Schmeltz, Cat. Mus. Godeff., v, p. 92. Pfeiffer, Mon. Hel., viii, p. 206. 
This small and well-characterized species is restricted to the lower portion of Pirai 
valley, on the northwest coast of Tahiti, where it is abundant on foliage. Pfeiffer’s 
“habitat in insulis Navigatorum ” (— Samoa Isles) is decidedly wrong. The type is 
peculiar to the Society Isles. 
It is a solid, ovate-conic, chestnut-colored shell, marked by longitudinal cinereous 
strigations, and constant tuberculiform parietal tooth. The aperture is rather small, 
semi-oval, considerably contracted by the white, convex outer lip. It is never 
encircled by bands. Examples of a pale straw or flesh tint are not infrequent. 
P. ciTRINA, Pease. Plate III, fig. 52. 
Partula citrina, Pease, Amer. Jour. Conch., 1866, p. 195; Proc. Zool. Soc., 1871, p. 473. 
Schmeltz, Cat. Mus. Godeff., vi, p. 81. Pfeiffer, Mon. Hel., viii, p. 200. 
Partula faba, var., Carpenter, Proc. Zool. Soc., 1864, p. 675. Hartman, Cat. Part., p. 6; 
Obs. Gen. Part., Bul. Mus. Com. Zool., ix, pp. 180, 195. 
This fine arboreal species is restricted to a single valley, called Uparu, on the west 
coast of Raiatea. I found it abundant in a limited area in the upper portion of the 
valley. A few stragglers occurred lower down in company with faba and Garrettii. 
Though considered by some authors to be a variety of P. faba, I am, nevertheless, 
fully convinced of its specific value. When I first discovered it in 1861, I took but 
few examples, in consequence of not penetrating far enough into the valley to find its 
headquarters. A more extended research in 1873 revealed its specific centre, and I 
took about eight hundred specimens in various stages of growth, and many of the 
adults were in a gravid condition. 
All of my first collection passed into Mr. Pease’s possession, and were so few that 
I labeled them ‘a somewhat rare species.” There is not the least doubt that the 
more slender pale varieties of faba have repeatedly been confounded with and distrib- 
uted under the name of citrina. 
It has been suggested that it may be a hybrid between /uba and some other species. 
I only noticed fuba and Garrettit in the lower part of the valley, and not in the upper 
portion, which is the principal haunt of citrina. 
My largest examples are 25 mill. in length and 12 in diameter. It is always of a 
straw-yellow color, rarely with faint longitudinal darker strigations, and is either lemon- 
yellow or light red at the apex. It is never spirally banded, and the parietal wall is 
invariably edentate. The oblong white aperture is, including the peristome, half the 
length of the shell. The ivory-white lip is broadly expanded, planulate, declivous, 
