2D4 MAZATLAN UNIVALVES 



growth in the lower part ; towards the apex stained with 

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

 from pure snow white 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. 1*5, alt. '98. 



Afiatsp. 1-3, 1'13, *27. 



Hob. (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 ; IS 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 shelving 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 surface. 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. tortoiseshell pattern. 1460, 4 

 do. tortoiseshell changing into dark brown. 



GENUS CALYPTE^EA, Lam. 



Calyptrsea auct. (pars.) Subgen. Calyptraea, b. Les. Brod. 

 Calyptra, Humph. 1797, (pars). Gray, Proc. Zool. Soc. 1847, 



p. 157, no. 271. J5T. # A. Ad. Gen. i. 364. 

 Mitrularia, ScJmm. 1817, J2ss. no. 9. Phil. Handb. Conch. 



p. 186. 

 Lithedaphus, Owen, Proc. Zool. Soc. 1842, p. 147. Litholepas, 



Gray, loc. cit. 

 Cemoria, ~Risso< 1826 ; non Leach, nee Swains. 



