270 UNITED STATES GEOLOGICAL SURVEY OF THE TERRITORIES. 



TECTIBRANCHIATA. 



BULLID-ffi. 

 Genus HAMINEA, Leach. 



Synon. — Bulla (sp.), of many authors, but Dot as restricted. 



Hamincea (Leach, MS.), Gray (1847), Ami. Mag. N. H., XX, 268; without a description. 

 Baminea, Gray (1847), Proceed. Zoiil. Soc, 161.— H. and A. Adams (1854), Genera Recent Moll., II, 

 16.— Chenu (1859), Man. Conch., I, 390— Stoliczka (1868), Palajont. Indica, II, 429. 



Etijm. — Hamus, a hook; from the curved form of the aperture. 

 Type. — Bulla hydatis, Linn. 



Shell thin, ventricose, oval or subglobose, involute, in the recent state 

 corneous, flexible, and without coloration ; surface transversely striated, and 

 usually covered with a thin epidermis; aperture as long as the shell, narrow 

 posteriorly, widened and entire below; inner and outer lips simple; spire 

 hidden. 



The shells of this genus are very similar in form to those of Bulla, but 

 are always transversely striated, and much thinner; those of that genus and 

 Atys, another allied type, being solid. The animal of Haminea differs from 

 that of Atys, and agrees with Bulla, in having well-devekrped eyes. It, 

 however, envelops the shell more completely than in either of those types, 

 and presents some other differences of anatomical details, which are, of 

 course, not directly available to the palaeontologist in dealing with fossil 

 species. Like Bulla, these mollusks inhabit the muddy bottoms of estuaries, 

 and feed on bivalves. 



Many conchologists, and nearly all palaeontologists, make no distinction 

 whatever between this group and Bulla proper, of which it might, perhaps, 

 without impropriety, be regarded as a subgenus. It seems to' range back to 

 the Cretaceous at least — ranges through the Tertiary rocks, and is well 

 represented among the mollusks of the present epoch. 



I am much puzzled in regard to the Cretaceous species here referred to 

 this genus. They certainly differ from Bulla proper in their less solid and 

 constantly transversely-striated shell. It is true, Haminea and Bulla are both 

 regarded as rather estuary than marine types; while the species here under 

 consideration are found associated with marine shells only. This, however, 

 may have resulted from their dead shells being carried by currents from 

 estuaries into salt-water, or, possibly, from the species having become 

 naturalized in the latter. These shells also closely resemble some forms 

 referred by high authorities to the genus Atys, particularly the group Roxavla 



