376 PROCEEDINGS OF THE ACADEMY OF [May, 



A NEW SPECIES OF ONCHIDIOPSIS FROM BERING SEA. 

 BY WILLIAM H. DALL. 



The 'genus Onchidiopsis Bergh (1853) was proposed for certain 

 Arctic mollusks related to Velutina and possessing an internal nearly 

 laminar shell. The minor characters of the few species known are 

 in many respects different but their combinations are so intermixed 

 that it is difficult to assign to the differences more than specific 

 value. However the peculiarities of the present species are such 

 that I venture to separate the genus into two sections, as follows : 



Genus ONCHIDIOPSIS Bergh, 1S53. 



Section ONCHIDIOPSIS, type 0. gronlandica Bergh. 

 Adult animal with an impervious notseum. 



Section ATLANTOLIMAX, type 0. (A.) hannai Dall. 

 Adult with a large dorsal foramen in the notseum. 



Onchidiopsis <Atlantolimax> hannai n. sp. 



Animal, after preservation in spirits, of a yellowish white color 

 except on the sides of the foot and on the osphradium. The foot is 

 muscular, broad, tapering and bluntly pointed behind, extending 

 about one-third of its length behind the hinder margin of the no- 

 tseum even when contracted; the front edge duplex, auriculate at 

 the anterior lateral angles; proboscis entirely retractile within a 

 transverse slit, below the short stout tentacles; eyes black, distinct, 

 completely imbedded in and a little above the not perceptibly swollen 

 bases of the tentacles, on their outer sides; verge situated behind 

 the right tentacle, large, twisted, at first stout and subcylindrical, 

 then deeply constricted; then compressed and expanded with a 

 conical papilla at the outer corner of the expansion 1 much as in 

 0. corys Balch. 



The sides of the foot are radially corrugated, the convex folds 

 sometimes more or less granulose; above the corrugated area and 

 in the pedal sulcus below the edge of the mantle the surface is smooth 



1 In Balch's figure of 0. corys this papilla is shown at the inner corner of the 

 expansion, a difference which is probably due to twisting. Cf. Proc. U. S. Nat. 

 Museum, No. 1,761, pi. 22, fig. 1. 



