372 MAZATLAN TTNIVALVES 



and C. cervus of Linn. The species was adopted for geo^aphi- 

 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 S. 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 t^e 

 species, are by no means constant. The Mazatlan shells rare y 

 develop inner dots; but the number of spots i^ extremely 

 variable, one specimen exhibiting on the abral half the numer- 

 ous small spots of C. cervus, on the labial half the dis ant oce - 

 lated spots of C. exanthema. The anterior dilation of the moutli 

 is also variable, generally taking the open form of C. c^^* 

 vinetta, but sometimes the narrower shape of G. exantnema. 

 The columellar indentation and markings are a so variaoie. 

 Sometimes the posterior labral deposit equals the labial, some- 

 times decidedly exceeds it, sometimes Mis still more below t 

 The size is very rarely small as i^. C cervinetta ; generaUy 

 elongated as in C. exanthema, occasional y large and swollen 

 as in C. cervus. The colour is either light or dark ; ^^th the 

 bands varying in distribution, and the mantle hne generaUy 

 staight, s'^^m^etimes waved. A swollen adolescent specimen 



measures ^^^^^it^' ^^^-SJ; 



A cylindrical sp. » "^ ^' " ^ " _ 



CTijA _W. Indies, passim. — Barbadoes, fossil. Dr. Cutting. 

 (C! cervinetta,) Panama and Taboga •, 115 sp. at and just 

 above low water mark of spring tides^mder stones 15-iO m^ 

 in diameter; C. B. Adams. -S. W. Mexico, common,* 

 p p. a— Mazatlan ; not uncommon ; L pool tot. 

 Tablet 1734 contains 3 sp. adolescent, banded.-l735, 1 do. 

 form cervns.-1736, 3 sp. spots beginning.-1737 3 sp. adult, 

 bands evident.-1738, 3 do. bands concealed.-l/39, 3 sp. adi^t, 

 light colour, spots very faint.-]74fl, 1 do. spots decided.-1741, 

 1 80 slightly spotted, not banded, resembhng C. talpa.-1744, 

 1 so right with few ocellated spots, left with close numerous 

 simple ones.-1743, 2 sp. with ocellated spots ; one smaU, type 



• T^flfnrn I was aware of the separation of C. exanthema and cerrinetta, I M- 



