FAUNA OF OETHAULAX PUGNAX ZONE. 81 



varices (a character used by Monterosato) preserve constancy. It 

 is, therefore, evidently a difficult task to divide the genus naturally. 



Eisso named no type, but the only species figured by him belongs 

 to the group afterwards called Leiostraca by H. and A. Adams. 

 Melanella Bowdich is monotypical; the species named by him M. 

 dufresnii is supposed to be that later called Eulima major Sowerby. 

 Eulima polita Risso's first species is a Melanella^ and a type must 

 therefore be selected from among the others, and his figured species 

 E. subulata Brocchi (and probably also of Donovan, 1804) is the 

 most appropriate. 



A tentative arrangement follows : 



Genus MELANELLA Bo^^^dich, 1822. 



Tyjye of the genus — Melanella dufresnii Bowdich. 



Shell white or colorless, usually solid, free living, with an ovoid 

 operculum with a small, partly spiral nucleus, the aperture holos- 

 iomate when adult, the whorls nearly or quite flat-sided, the suture, 

 appressed, the pillar and peristome simple and slightly thickened. 

 Animal with slender tentacles, the eyes sessile behind or slightly out- 

 side the tentacular bases, w^ith no epipodial lobes; a radula present; 

 the anterior margin of the foot double and squarely truncate; the 

 sexes separated. The parasitic and commensal species often with 

 certain organs degenerate, absent, or specially modified to suit their 

 mode of life. 



Subgenus MELANELLA sensu strictu. 



Characters as above stated, Balcis Gray, Vitreolina Monterosato, 

 and Acicularia Monterosato (1884, not Acicularia Adams, 1875) are 

 synonymous. 



Subgenus EULIMA Risso, 1826. 



Type. — Turho subulata Brocchi. 



Shell usually with colored bands or streaks, thin pellucid, straight, 

 the whorls axially wider than in Melanella^ acute, slender, the pillar 

 straight, the outer lip sharp, simple, the aperture elongate oval. 

 Animal and operculum much as in Melanella. 



Leiostraca H. and A. Adams, 1853, in part; Suhidaria Montero- 

 sato, 1884, in part; and Eulima (sp.) of Authors, are synonymous. 



Section HALIELLA Monterosato, 1880. 



Type. — Eulima stenostoma Jeffreys. 



Shell resembling Eulima s. s. (in the typical species colorless) but 

 with the columella distinctly twisted. The animal in the typical 

 species is blind. 



54907°— Bull. 90—15 6 



