OP CONCHOLOGY. 113 



operculum of the true Amycla (corniculum, Oliv.), of Adams, 

 which is a nassoid form, as shown by Troschel. 



A comparative diagnosis will best serve our purpose in dis- 

 tinguishing Amphissa versicolor and A. corrugata, which have a 

 somewhat similar facies. 



A. CORRUGATA. 



Shell of seven or more whorls ; covered with a rather thick 

 yellowish epidermis when perfect ; longitudinally plicated with 

 obsolete ribs which are evanescent on the lower half of the 

 whorls. In ordinary specimens there are twenty-five or thirty 

 of these plications, with a stout pinch behind the upper angle of 

 the aperture. The riblets are crossed by deep channelled grooves, 

 sparser and deeper on the lower half of the whorl, about thirty- 

 five on the last whorl. The riblets are nearly parallel with the 

 longer axis of the shell. 



• The columella is usually covered with a thick deposit of callus, 

 the outer edge of which is sharply raised above the whorl, form- 

 ing a sort of groove. Colors livid brownish, variegated with 

 irregular yellowish and brownish spots not well defined, some- 

 times livid rufous. 



Lon. 1-3 in. to -8 in., as extremes; lat. -5 in. to '35 in. as 

 extremes. 



A. VERSICOLOR, n. s. 



Shell of about five whorls, last whorl two-thirds the length of 

 the shell. Epidermis imperceptible ; shell ornamented with 

 rather strong sinuous ribs, which often invade the lower third of 

 the whorl; there are fourteen to sixteen of these on the last 

 whorl in well grown individuals, and they are crossed by rather 

 strong, thread-like lines, between broad channels on the con- 

 vexity of the whorls, which become narrower and groove-like on 

 the anterior part of the last whorl. They are about seventeen 

 in number, in average adult specimens, on the last whorl. Post 

 labial pinch almost obsolete, quite so in some specimens. Colors 

 very variable, pink, salmon color, livid bluish purple, brown 

 and pure white, all plain, or variously marked with a network 

 of white and brown lines, patches, dots, &c., &c. 



Columellar callus less prominent than in the last ; both have 

 the entire aperture striated internally in some fine individuals, 

 and often two or three tooth-like tubercles on the columella. 



Lon. -48 in. ; lat. -26 in. 



This species is the most common beach shell found at Mon- 

 terey. They are very uniform in size though so variable in 

 color. They live under and about the stones at and near low- 



