100 NILS ODHNEB, NORTHERN AND ARCTIC INVERTEBRATES. III. OPISTHOBRANCHIA ETC. 



of smaller ones. Gills 8, tripinnate, in a circle before the anus, retractile. Rhinophorial 

 apertures slightly granulate on the margin. Oral tentacles tuberc uliform, shortly acu- 

 minate, on the sides of the head. Foot rounded in front, with distinct transversal 

 furrow but without median incision; the posterior end scarcely overtopping the mantle. 

 Penis cylindrical, lengthened, unarmed. Colour rosy white, yellowish towards the 

 margin; the gills lemon-coloured. L. 50 mm. Br. 25 mm. 



Radula oc • • co ; the teeth uniform, compressed from the sides, with produced 

 arched spine, and inserted in the basal membrane with a thin edge. The smallest 

 ones situated furthest in and furthest out in the rows. The longest about 0,3 mm. 

 in length. 



Issa villosa n. sp. 

 PI. I fig. 21. 



Body as in I. lacera, but the papillae very numerous (in the dorsal margin about 

 40 — 50 on each side) and set in about 6 indistinct rows on the back; their length 

 varying, the longest about 5 mm. Gills 5, bipinnate (in one specimen 7). The 

 posterior end of the foot, which extends beyond the mantle, is rather long, about 

 7 e of the body. L. of the animal up to 48 mm. Colour yellowish white. 



Radula similar to that of I. lacera, 5 2 1 2 ■ 5 ; but the base of the largest 

 laterals is nearly quadrangular. 



Doridunculus pentabranchus n. sp. 



PL I figs. 22—23. 



Body 13 mm. in length, depressed, of a pale yellowish colour (in alcohol). 

 Mantle ovate, 7 mm. broad, extending far over the sides of the body, slightly bilobed 

 behind and covered all over with acute-conical papillse of varying size. The crests, 

 6 mm. in length, beginning a little before the rhinophorial apertures and running 

 backwards, parallel to each other, to the sides of the gills. The under surface of the 

 mantle furnished with radiating ribs. Gills 5, small, simply pinnate, in a semicircle 

 before the anus ; on the inner side of the hinder ones two minute papilla? (undeveloped 

 gills?). The foot narrow (3 mm.), its posterior end extending far (4 mm.) beyond the 

 mantle, covered with papilla? and furnished with a median crest which unites to the 

 posterior pallial margin. The rhinophorial apertures wide, without sheaths; the clubs 

 of the rhinophores laminated. The oral tentacles represented by broad side-lobes of 

 the head. Porus genitalis lateral, just below the base of the mantle, about 4 mm. 

 from its anterior margin. Colour yellowish brown. 



Radula 511011-5; the teeth with a quadrangular base and a projecting 

 spine; the inner laterals with 2—3 denticles on each side of the median spine; the 

 second laterals (from the rhachis) with a stronger spine and 2—3 denticles on its 

 outer side ; the rest of the laterals without denticles. 



