MAZATLAN UNIVALVES 271 



A long decked sp., margin to front *36, to lack '47. 

 A short do. '48, "3. 



Hab.(C. aculeata) W. Indies, passim, auct. Cuba, Sagra. 

 Honduras, Dyson. Brazils : Patagonia ; D' Orbigny. Ben- 

 guela ; 1 sp. in excellent preservation ; Tarns. Table Bay, 

 Krauss. Cape Natal, Mus. Cuming. Isle of France, Fav- 

 anne. Kurachee, Mouth of the Indus, Mus. Cuming. Port 

 Jackson, Rev. It. L. King. New Zealand, Rev. It. Taylor. 

 Sydney and Swan Eiver, Mus. Cuming. (Dark var.) Japan, 

 Mus. Cuming. (Light var.) Chili, Capt. Ld. Byron. (C. 

 echinus, &c ? ) Lobos Is. Peru, Cuming. Panama; under stones 

 at low water, rare ; C. B. Adams. (C. Calif ornica) Monterey, 

 common, Nuttall. Mazatlan ; common, on shells &c. ; 

 young shells abundant on Chamse and Spondyli ; L'pool Col. 

 Tablet 1321 contains 10 sp. extremely young. 1322, 7 do. a 

 stage older, with a fragment to shew the inner surface of the 

 deck. 1323, a young deformed shell, nearly smooth, probably 

 belonging to this species. 



Specimens illustrating form and sculpture. Tablet 1324 con- 

 tains 8 sp. (var. hystrix) of different ages. 1325, 13 sp. do. 

 (var. echinus.) 1326, 8 sp. do. finely aculeate, arched. 1327, 

 10 sp. do. flat, (one of the young in situ on an adult.) 1328, 8 

 sp. do. spiny processes 'imperfectly developed. 1329, 4 sp. do. 

 (var. Calif ornica.) 1330, a series of 12 sp. shewing gradations 

 between the above forms. 1331, 7 sp. shewing gradations from 

 flat to arched. 1332, 6 sp. shewing gradations in amount of 

 spiral involution. 1333, 5 sp. shewing gradations in size of 

 deck. 1334, 6 sp. shewing gradations in prominence or sinking 

 of deck. 



Specimens skewing shape of deck. Tablet 1335 contains 3 sp. 

 center pointed, sides much swollen. 1336, 4 do. sides swollen. 

 1337, 3 do. sides slightly swollen. 1338, 3 do. center 

 rounded. 1339, 1 do. point turned outwards .1340, 4 do. form 

 approaching C. nivea. 1341, 3 do. deck partially opaque. 



Specimens displaying changes of colour. Tablet 1342 contains 

 2 sp. (hystrix and echinus) pure white. 1343, 10 sp. variously 

 shading into brown. 1344, 11 sp. , do. dark lustrous brown. 

 1345, 12 sp. tortoiseshell, variously mottled. 1346, 5 do. whiter 

 tint. 1347, 6 do. more or less tinged with green. 



Distorted specimens. Tablet 1348 contains 7 sp. of irregular 

 shape. 1349, 7 sp. diseased by worms. 1350, 3 sp. with addi- 

 tional margin. 1351, 4 sp. passing towards C. nivea. 1352, 3 

 sp. passing towards C. onyx. 



