102 NILS ODHNEB, NORTHERN AND ARCTIC INVBRTEBRATES. III. OPISTHOBRANCHIA ETC. 



Head with the sides considerably expanded and appearing as somewhat inflated. 

 Oral tentacles very small, papilla-shaped, connected by a low transverse cu.taneous 

 fold, running in a curve across the head. 



Rhinophores smooth, very long and slender, united at the base. 



Papillee set on 12 — 13 obliquely- transverse ridges, one row on each ridge, the 

 foreniost situated. m front of the rhinophores, the largest containing about 8 or 9 

 papillee. Between the 6th and 7th ridges there is a larger interspace for the latero- 

 dorsal anus, which is situated close in front of the 7th ridge. 



Penis furrow-shaped, of uniform breadth, unarmed. 



The female genital aperture is dilated to a bursa copulatrix, the upper and 

 lower margin of which is armed with a circular cushion, furnished on the periphery 

 with 12 small hooks. 



Bulbus pharyngeus short and broad, its inferior margin longer than the superior, 

 both convex; the posterior part concave. The lips only a little projecting. 



Mandibulse with one row of bicuspidate or tricuspidate denticles on the anterior 

 margin; the processes short, neaiiy smooth. 



Radula 111 with about 17 rows; the sides of the median teeth and the 

 inner margins of the lateral ones are armed with about 20 rather strong denticles. 

 Colour of the teeth påle yellowish brown. . 



