H2 LAND AND FRESH WATER MOLLUSKS 



Family ONCHIDIID^E. 

 Genus Onchidium Buchanan, 1800. 

 Type Onchidium typhcz Buchanan, Trans. Linn. Soc., v, p. 132, 



1800. 



Subgenus Onchidella Gray, 1850. 



Type Onchidium nigricans Quoy, Fig. Moll. An., iv, p. 117, pi. 

 181, fig. i, 1850 (selected as type by Herrmannsen, Ind. Gen. Mai., 

 Suppl., 1852). 



Dorsal surface without arborescent processes, margin of the mantle 

 with prominent spaced papillae, serving as conduits for mucous glands ; 

 lower surface of the mantle with muciparous glands ; dorsum with 

 dorsal eyes ; mouth agnathous. Warmer seas. 



Section ARCTONCHIS Dall, nov. 



Species small, like Onchidella, but without muciparous glands on 

 the lower side of the mantle, without dorsal eyes and with a jaw. 

 Cool temperate and boreal coasts. 



Type Onchidella borealis Dall. 



I had long since proposed to retain for this group the name Onchi- 

 della, supposing that name to be practically a synonym of Onchidium. 

 This, however, is not now regarded as allowable, and Onchidella must 

 follow the fate of its type. 



I propose therefore the sectional name Arctonchis for the group of 

 small boreal Onchidella which includes at least O. borealis and 

 O. celtica Forbes and Hanley. 



Onchidella (Arctonchis) borealis Dall. 



Onchidella borealis DALL, Am. Journ. Conch., vn, p. 135, 1871. W. G. 

 BINNEY, Proc. Acad. Nat. Sci. Phila., 1876, p. 84, pi. vi, figs. E, EE, 

 Sept., 1876. BINNEY, Terr. Airbr. Moll. U. S., Third supple., Bull. 

 Mus. Comp. Zool., xix, No. 4, pi. vi, figs. D, E, 1890 (called carpenteri 

 by error, in text pp. 214, 224) ; Fourth Supplement, Bull. Mus. Comp. 

 Zool., xxn, No. 4, p. 202, 1892. 



Onchidium boreale DALL, Semper, Arch. Phil. Bd. 3, heft vi, p. 282, pi. 

 xxi, fig. 13. 



Range. California to Bering Sea on the N. W. coast of America. 



California (Binney) ; Coos Bay, Oregon (Hemphill) ; Victoria, 

 Vancouver Island ! Lituya Bay ! Port Mulgrave ! Port Etches ! Una- 

 laska ! and Port Moller on Bering Sea ! in Alaska. 



Observations on this species have been published by the writer, Mr. 

 W. G. Binney, Semper, and Henry Hemphill ; and, as their articles 

 are short and widely scattered in the literature, an abstract of the 



