372 MAZATLAN UNIVALVES 
and C. cervus of Zinn. The species was adopted for geographi- 
cal reasons by Prof. Adams, who regarded all the W. Indian 
shells as C. exanthema, all those from the W. coast as C. cer- 
vinetta, and all those from the Polynesian islands as C. cervus 
(=cervina). While however the 8. W. Mexican shells belong 
clearly and exclusively to the type C. cervinetta, those from 
Mazatlan belong with almost equal exclusiveness to the typical 
C. exanthema. An examination of several hundred specimens 
shews that the characters usually relied on to separate the 
species, are by no means constant. The Mazatlan shells rarely 
develop inner dots; but the number of spots is extremely 
variable, one specimen exhibiting on the labral half the numer- 
ous small spots of C. cervus, on the labial half the distant ocel- 
lated spots of C. exanthema. The anterior dilation of the mouth 
is also variable, generally taking the open form of C. cer- 
vinetta, but sometimes the narrower shape of C. exanthema. 
The columellar indentation and markings are also variable. 
Sometimes the posterior labral deposit equals the labial, some- 
times decidedly exceeds it, sometimes falls still more below it. 
The size is very rarely small as in C. cervinetta; generally 
elongated as in C. exanthema, occasionally large and swollen 
asin C. cervus. The colour is either light or dark ; with the 
bands varying in distribution, and the mantle line generally 
straight, sometimes waved. A swollen adolescent specimen 
measures j long. 3°44, lat. 2°04. 
A cylindrical sp. TOTO, ee cOUs 
Hab.—W. Indies, passim. —Barbadoes, fossil, Dr. Cutting.— 
(C. cervinetta,) Panama and Taboga; 115 sp. at and just 
above low water mark of spring tides, under stones 15-20 in. 
in diameter; C. B. Adams.—S. W. Mexico, common,* 
_ P. P. C—Mazatlan ; not uncommon; L’pool Col. 
Tablet 1734 contains 3 sp. adolescent, banded.—1735, 1 do. 
form cervus.—1736, 3 sp. spots beginning.—1737, 3 sp. adult, 
bands evident.—1738, 3 do. bands concealed.—1739, 3 sp. adult, 
light colour, spots very faint.—1740, 1 do. spots decided.—1741, 
1sp. slightly spotted, not banded, resembling C. talpa.—1742, 
1 sp. right with few ocellated spots, left with close numerous 
simple ones.—1743, 2 sp. with ocellated spots; one small, type 
* Before I was aware of the separation of C. exanthema and cervinetta, I un- 
fortunately mixed some small specimens of the latter from the S. W. Mexican 
collection with those from Mazatlan, (the box from the latter having been 
temporally mislaid,) and distributed them accordingly. Those of the true C. cer- 
vinetta type were extremely*rare in the Mazatlan collection, 
