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



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

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

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

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

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

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



Radula go ■ O • go ; the teeth uniform, compressed from the sides, with produced 

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

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

 in length. 



Issa villosa n. sp. 

 PI. I tig. 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 

 Vfi 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 pentahranclms n. sp. 

 Pl. I figs. 22—23. 



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

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

 behind and covered all över with acute-conical papillae of varying size. The crests, 

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

 backwards, parallel to each otlier, 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 papillse (undeveloped 

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

 mantle, covered with papillae 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 5-11011-5; 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. 



