29i MAZATLAN UNIVALVES 



growth in tlie lo^er part ; towards the apex stained with 

 chesnut in the dark shells. The colour of the interior varies 

 from pure suow -.vhite to very dark brown ; generally more or 

 less spotted or rayed with chesnut. The finest specimens 

 ■were eagerly caught up by collectors : the largest I could 

 find measures long. 1'72, lat.l'^, alt. '98. 



Aflatsp. „ 1-3, „ 1-13, „ -27. 



Sab. — (C. tenuis) Samanco Bay, Peru ; on living shells, in mud- 

 dy sand, 9 fm. ; Cuming. — (C. hispida) Isl. Muerte ; on dead 

 shells, in sandy mud, 12 fm. ; Cuming. — C. maculata) Do. 

 11 fm. Cuming. — Panama ; under stones at low water mark, 

 rare ; C. B. Adams. — San Diego, Lieut. Green. — Monterey ; 

 very rare ; Nuttall. — Mazatlan ; not uncommon ; L'pool Col. 



Tablet 1445 contains 3 sp. extremely young. — 1446, 3 do. a 

 stage older.— 1447, 4 do. adolescent : on one a young Crepidula 

 aculeata has fastened itself, wearing away the spines. — 1448, 

 1 sp. adult, with attachment of another. 



Specimens slieiving form. Tablet 1449 contains a series of 9 

 sp. from very flat to conical. — 1450, 3 sp. shewing crenations of 

 the margin. — 1451, 4 do. margin very irregular. — 1452, 4 sp. 

 curiously deformed and thickened by disease . 



Specimens shewing changes of surf ace. Tablet 1453 contains 

 3 sp. nearly smooth. — 1454, 4 do. tubercular spines develop- 

 ing. — 1455, 4 do. spines regular and crowded. — 1456, 6 sp. some 

 spines greatly developed. 



Specimens shewing colour. Tablet 1457 contains 4 sp. white, 

 developing chesnut rays. — 1458, 5 do. light brown, scarcely or 

 generally diffused. — 1459, 4 do. tortoisesheU pattern. — 1460, 4 

 do. tortoisesheU changing into dark brown. 



Gbnus CALYPTEiEA, Lam. 



Calyptrsea auct. (pars.) Subgen. Calyptrsea, b. Less. Brod. 

 Calyptra, Humph. 1797, (pars). Grat/, Proc. Zool. Sac. 1847, 



p. 157, no. 271.— S". ^' A. Ad. Gen. i. 364. 

 Mitrularia, Schum. 1817, JEss. no. 9.— Phil. Hartdb. Conch. 



p. 186. 

 Liihcdaphus, Owen, Proc. Zool. Soc. 1842, p. 147.— Litholepas, 



Gray, loc. cit. 

 Cemoria, jRisso, t826 ; non Leach, nee Swains. 



