GASTEROPODS 387 



patenes and spots adorn the outer lip. The shell is from two to two 

 and a half inches long 1 . (Plate LXXIII.) 



P. Jtartnatitoittfi. 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 occurs 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 length. 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 LXXIII.) 



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. 



