1P> NILS ODHNER, NORTHERN AND ARCTIC INVERTEBRATES. III. OPISTHOBRANCHIA ETC. 



b. Spire prominent; shell elongated; outer lip a little compressed above. 

 Head-lobe deeply incised behind. L. 17 mm, animal; 7 mm, shell; 

 imeini denticulated 



Ph. lima (Brown 1827) lineolata (Oouthouy 1839). 

 Uncini smooth ; sculpture consisting of distinct points without 

 connecting lines var. frigida Knipowitsoh 1896. 



B. narrow, scarcely curved, 



1. on each side 6 (radula 6.1.0.1.6); shell striated. 



a. Shell latticed on the surface: outer lip scarcely compressed. Animal with 

 the mantle incised behind ; colour white, with opaque white spots. L. 17 

 mm, animal; 6 mm, shell Ph. pruinosa (Clark 1828). 



PI. Ill fig. 



//. shell with spiral sculpture only; outer lip highly compressed behind. L. 10 mm. 



Ph. flexuosa M. Saks 1870. 



2. on each side 2 (radula 2.1.0.1.2); shell smooth, very broad (like a Diaphana). Mantle incised 

 behind. L. 2,s> mm, shell Ph. velutinoides Gr. (). Saks 1878 — ? ventricosa (Jeffreys 1867). 



Fam. Aplysiidae. 



1 . Parapodial lobes separated in front (subfam. Aplysiina?). Rhinophores placed be- 

 fore the ends of the dorsal lobes; mantle open at the back; body smooth; ra- 

 dula cc . 1 . od Aplysia Linne. 



2. Parapodial lobes separated only by the genital groove (subfam. Dolabriferinse). Rhinophores as in Aplysia; 

 mantle closed, without dorsal opening; body mostly rough or warty : radula » . 1 . oo Dolabrifera Gray. 



Aplysia Linne 1760. 

 Tethys Linne 1758. 1 



Rhinophores and tentacles cylindrical with a longitudinal furrow in front. Co- 

 lour dark-reddish, brownish or greenish with white dots. Shell an ovate, concave 

 plate of a pale yellowish colour. L. 70 — 150 mm, animal; 17 mm, shell 



A. rosea Rathke 1799 = punctata Cuvier 1803. 



PL 11 figs. 4—7. 



Dolabrifera Gray 1847. 



Body elevated: tentacles and rhinophores very low and widely expanded. Colour dark olive-brownish, 

 the body-sides and the sole darkest, the sides of the hack with reddish brown spots. Shell elongated, truncated 

 in front, with a prominent spire: its colour pale yellowish. L. 2."» mm. animal: 10,5 mm. shell 



I). Kollhörn Bekgh 1872. 



Fam. Pleurobranchidae. 



Pleurobranchus Cuvier 1804. 

 Radula oo . 2 . oo . Tentacles replaced by a velum. 



Gill-plume pectinated with about 20 teeth on each side; rhinophores cylindrical, 



1 The name Tethys was applied by Linne in 1766 to a Nudibranch. 



