GASTEROPODS 387 
patenes and spots adorn the outer lip. The shell is from two to two 
and a half inches long. (Plate LX XIII.) 
P. hemastoma. Like its relative, P. lapillus of Northern waters, 
this species is so variable as almost to defy description. The form 
that usually occurs from Hatteras to Florida is of a bluish-gray color, 
and is indistinctly encircled with narrow yellow zones, which are crossed 
by somewhat vague longitudinal waves of black. The columella and 
outer lip and interior are orange-yellow. The spire is moderately high, 
with a sharp apex. The whorls are noduled upon the shoulder. There 
are revolving grooves throughout, even within the aperture. A Texan 
variety of this species has a much more elevated spire, with channeled 
sutures, and small aperture of bright salmon-color. 
Upon the Californian coast there are three species of Purpura, which 
markedly resemble the:P. lapillus of the Maine shores. Their extreme 
variability has given rise to much confusion in their nomenclature; 
the multitude of names given by numerous authors to the varietal forms 
of these three species constitute a list of synonyms which is appalling 
to the systematic student. 
P. crispata. With very few modifications, a description of P. la- 
pillus would apply to this species, which oceurs commonly at San Fran- 
cisco and ranges north. Crispata is possibly. heavier, with a smaller 
aperture, and with four or five round teeth upon the inner white surface 
of the thickened outer lip. It ranges in color from pure white to dark 
brown and is sometimes banded. The surface may be smooth or rough, 
and is sometimes ruffled all over with wrinkled frills. Length one and 
a half inches. Its habits and station are much the same as those of 
P. lapillus, of which it is possibly a descendant, somewhat modified by 
changed environment. (Plate LXXIII.) 
P. lima. A less common species, with rounded whorls and channeled 
suture, and about fifteen spiral grooves upon the whorls. The color is 
light brown; the length from one quarter of an inch to one inch. 
P. saxicola. <A shell exceedingly abundant along the whole Cali- 
fornian coast, living under quite the same conditions as the purpuras 
already described. It is smaller than the last two, being always less 
than an inch in jength. It also runs through the gamut of variations as 
to color-scheme and sculpturing, but always preserves a certain indi- 
viduality. There is a tendency to a small umbilicus; the outer lip is 
sharp; the columella is flattened and slightly twisted; and anterior canal 
is short, and bears to the left. A smaller aperture, with relatively thicker 
shell, seems to be all that distinguishes it from the smaller varieties 
of the east-coast species. (Plate LX XIII.) 
Genus Monoceras 
This genus, which is very closely allied to Purpura, is almost 
wholly confined to the west coast of the United States. The 
name is given on account of a peculiarity, which has, however, 
already been noticed in Cerostoma, namely, a horn-like projection 
from the basal portion of the outer lip. In all other respects 
this genus is nothing but a true Purpura. 
