MAZATLAN UNIVALVES 353 



1695, 3 sp. curiously mended. 1696. 1 do. supporting 3 speci- 

 mens of Ostrea conchaphila round its base. This, with several 

 other specimens, retains its operculum. 1697, 2 separate 

 opercula. 



402. MODULUS , sp. ind. 



Tablet 1698 contains a solitary and young shell resembling 

 M. catenulatus in outline and tooth ; but with a weljrdeveloped 

 umbilicus, rounded and distinctly tuberculous ke'l, and whirls 

 concave above. The colour is prettily mottled with purplish 

 brown. It differs from M. disculus in the small tooth, conical 

 spire and concave whirls. Long, '47, long. spir. "3, lat. '5, 

 div. 80. 

 Hob. Mazatlan ; 1 sp. with M. catenulatus ; L'pool Col. 



403. MODULUS DISCULUS, Phil. 



Trochus disculus, Phil, in Kust. Mart. no. 308, p. 242, pi. 36, 



f. 14 :Zeit.f. Mail. 1846, p. 51, no. 19. 

 Modulus disculus, H. fy A. Ad. G-en. i. 317. 

 = Modulus duplicatus, var. A. Ad. in Mus. Cum. 

 = Modulus dorsuosus, Gould, (ad fid. sp. typ.) Mex. Sf Cat. 



Shells, p. 10, pi. 14, f. 12. 

 Comp. Monodonta modulus, Lam. in Kust. Mart. no. 307, 



p. 241, pi. 36, f. 1113. (JTab.W. Indies.) 



Known from M. catenulatus by the depressed spire, some- 

 what rounded and strongly tuberculous keel, violet-tinted 

 mouth, and very deeply cut tooth, with a broad groove on the 

 base. The young specimens are imperforate, but the old ones 

 have a small umbilicus. It most closely resembles one of the 

 W. Indian species. Long. '6, long. spir. '32, lat. '65, div. 110. 

 Sab. Mazatlan, Philippi. Do. ; 3 sp. with M. catenulatus ; 



L'pool Col. "Found at Acapulco, Col. Jewett" Gould. 



Tablet 1699 contains a young and an adult specimen. 



GENUS FOSSABUS, Adanson. 



Fossar, Gray, Syn. 1840: Proc. Zool. Soc. 1847, p. 151, 



no. 206, (Forsar, err. typ.) 

 Fossarus, Phil. Arch. f. Nat. i. p. 42, 1841 iffandb. Conch. 



p. 173. 



