202 MAZATLAN UNIVALVES 



distinct radiating black lines. Sometimes the internal surface 

 is beautifully mottled with purple or brown. The animal 

 mark is by no means constant in shape ; but, when well denned, 

 shews the body gathered pretty regularly into points with 

 curves between. The smallest specimen is about '25 in length ; 

 the largest measures long. 2 '15, lat. 1'7, alt. '72 

 Hab Mazatlan, Lieut. Shipley $. W. Mexico, P. P. C 



Mazatlan very common ; Lpool fy Havre Coll. 



Tablet 923 contains 4 sp. various ages. 924, 4 specimens 

 white. 925, 5 do. greenish tinge. 926, 4 do. coloured within. 

 927, 4 do. tortoiseshell. 928, 8 sp. yellowish tinge. 929, 4 do. 

 very faint appearance of marginal dots. 930, 7 do. a shade 

 more developed. 931, 8 sp. black rays coated over. 932, 7 sp. 

 black dots distinct. 933, 7 do. more distinct. 934, 7 do. well 

 developed. 935, 5 sp. faint black dotted margin. 936, 5 do. 

 distinct black margin. 937, 6 sp. with brown tortoiseshell 

 markings. 938, 5 do. purplish tinge. 939, 4 do. black and 

 brown. 940, 3 sp. body mark distinct. 941, 3 sp. margin 

 abnormally indented. 942, 5 sp. irregular internal growth. 

 943, 1 do. with large Balanus, Lithophagus, &c. 



GENUS NACELLA, Schum. 

 Patella, pars, auct. 



262. NACELLA, -- , sp. ind. 



Tablet 944 contains a solitary specimen of a Nacella, of the 

 shape and size of Ancylus fluviatilis, with the apex spirally 

 recurved, and of a dark horny colour. It is not perfect enough 

 for description. 

 Hal. Mazatlan ; off Chama, 1 sp. ; L'pool Col. 



FAMILY 



GENUS ACM^EA, Esch. 



Eschscholtz Zool. Ail. ed. Rathlce, 1833, p. 16, (diagnosi copiosa.) 



Forbes fy Hani. Br. Moll. vol. ii. p. 434. Woodio. Man. 



Moll. p. 155. Phil. Handb. Conch, p. 199. (Non Acme, 



Hartm. 1821.) 



Lottia, Gray in Phil. Trans. 1833, and in Sow. Gen. 1833. 

 Patelloida, Quoy fy Gaim. 1834, Voy. Astr. vol. iii. p. 349. 

 Tectura, Audouin fy Milne Edw. Ann. Sc. Nat. 1830, vol. xxi. 



p. 226, (Gray : p. 325, PMLJH. $ A. Ad. Gen. vol. i. p. 458. 



