TRUNCATELLA 
A genus of unisexual, amphibious, snails, mostly tropical. 
They occur near the sea, on sea-weeds thrown up on the 
shore, among rocks, or in shallow water. Animal with eyes 
at the rear of the base of the two contractile tentacles. Shell 
small, eylindrie or pupoid, with small oval aperature and 
thin spiral operculum. Whorls transversely ribbed. As the 
animal approaches maturity, the upper portion of shell 
breaks off, the animal closing up behind it with a calcareous 
deposit when it abandons the outgrown parts. On account 
of this truncation of the shell, the genus has received its 
name. About 100 species have been described. Named by 
Risso. 
80 Truncatella californica 
Shell imperforate, thin, translucent, slightly striate; de- 
ciduous part of about 5 whorls, acute, gradually enlarged to 
a maximum of 2 mm; the mature shell usually of about 4 
whorls, quite convex, the last one not carinate below; aper- 
ture vertical suboval, lip simple, continuous, slightly ex- 
panded; mature shells of a maximum diameter of 2 mm, 
and length of 5, the whorls nearly uniform. The young 
shells attain a length of 5 mm before it begins to cast off 
its outgrown whorls. 
Type locality: San Diego, California. 
In November, 1913, the writer turned over a discarded 
coat on the edge of a flat subject to tidal overflow from the 
waters of San Diego bay, and in a space of about a cubic 
foot, in the folds of the coat, and in the honey-combed mass 
of decaying sea-grass beneath, discovered a colony of fully 
10,000 of these beautiful shining, amber-colored shells, the 
white animals being quite lively, and in all stages of de- 
velopment. 
Not rare at Santo Domingo, Baja Cal. 
81 Truncatella stimpsonii 
This I found in considerable numbers in company with Pedi- 
pes unisulcatus, on and under smoothly-worn boulders in caves 
on the ocean beach south of La Jolla, Cal., near high water mark. 
Very common at Santa Domingo, Baja Cal. 
82 Pomaulax undosus 
Shell 4 inches or more in height and diameter; shell of whitish 
pearl covered with a brown, fibrous epidermis; operculum horny 
within, outside strengthened with two heavy, curved ribs; whorls 
varied by numerous wavy ridges, and base ornamented with 
beaded circles. 
Santa Barbara, Cal., to Cape San Lucas; common at San Diego 
and at Santo Domingo, Baja Cal. Cedros Island. 
Quaternary:—-Santa Barbara, Cal., to San Quintin, Baja Cal.; 
Borrego Springs, Colorado Desert. 
