MAZATLAN UNIVALTES 353 



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

 mens of Ostrea conchapliila round its base. This, -vritli several 

 other specimens, retains its operculuni. — 1697, 2 separate 

 opercula. 



402. MoDXiLUS , sp. ind. 



Tablet 1698 contains a solitary- and young shell resembling 

 M. catenidatus in outline and tooth ; but with a well developed 

 umbilicus, rounded and distinctly tuberculous keel, and whirls 

 concave above. The colour is prettily mottled with purplish, 

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

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

 div. 80". 

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



403. Modulus disculus, Phil. 



Trochus disculus, PJdl. in Kust. Mart. no. 308, p. 243, pi. 36, 



f. U:—Zeit.f. Mai. 18i6, p. 51, no. 19. 

 Modulus disculus, S. Sf A. Ad. Gen. i. 317. 

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

 = Modulus dorsuosus, Gould, (ad fid. sp. typ.) Mex. 8f Cal. 



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

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



p. 211, pi. 36, f. 11—13. {Eah.—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 iimbdicus. It most closely resembles one of the 

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



Hah. — Mazatlan, Philippi. — Do. ; 3 sp. with M. catenulatus ; 

 L'pool Col. — "Found at Acaj)ulco, Col. Jetoett," Gould. 



Tablet 1699 contains a young and an adult specimen. 



Genus FOSSAEUS, Adanson. 



Fossar, Gray, Syn. 1810: — Proc. Zool. Soc. 1847, p. 151, 



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

 Fossarus, Phil. Arch. f. Nat. i. p. 42, 1841 : — Jlandh. Conch. 



p. 173. 



