GASTEROPODA. 333 



eacli side of tlie back ; mouth armed "witli liomy jaws ; stomach 

 simple, liver compact. 



Distribution, 13 species. Norway and Britain. Under stones 

 at low water, — 25 fathoms. T. Homhergii, Cuvier, found on 

 the scallop-banks, attains a length exceeding 6 inches. 



SCTLL^A, L. 



Type, S. pelagica, PI. XIII., Pig, 8. 



Etymology, scyllaea, a sea-nymph. 



Animal elongated, compressed ; foot long, narrow, and chan- 

 neled, adapted for clasping sea-weed; back with 2 pairs of 

 wing-like lateral lobes, bearing small tufted branchiae on their 

 inner surfaces ; tentacles dorsal, slender, with lamellated tips, 

 retractile into long sheaths ; lingual teeth 24.1.24, denticulated ; 

 gizzard armed with horny, knife-like plates ; orifices on the 

 right side. 



Distribution, 7 species. Atlantic, South Britain, Mediter- 

 ranean. On floating sea-weed. 



Nerea (punctata). Lesson, New Guinea ; 10 lines long, with 

 ear-shaped tentacles, and 3 pairs of dorsal lobes. 



Tethys, L. 



Etymology, tethys, the sea (personified). 



Synonym, Fimbria, Bohadsch. 



Type, T. fimbriata, L., PI. XIIL, Pig. 9. 



Animal elliptical, depressed ; head corered by a broadly ex- 

 panded, fringed disk, with 2 conical tentacles, retractile into 

 foliaceous sheaths ; gills slightly branched, a single row down 

 each side of the back ; reproductive orifices behind first gills, 

 vent on right side, behind second gill ; stomach simple. 



Distribution, 1 species. Mediterranean. Attains a foot in 

 length, and feeds on other molluscs and crustaceans. (Cuvier.) 



? BoRNELLA (Gray), A. Adams. 



Type, A. Adamsii, Gray. Length, 4 inches. 



Animal elongated ; dorsal tentacles retractile into branched 

 sheaths ; head with stellate processes ; back with two rows of 

 cylindrical, branched, gastric processes, to which small dendritic 

 gills are attached;* foot very narrow. 



Distribution, 3 species. Straits of Sunda, on floating weed ; 

 Borneo. 



• This observation deserves further inquiry. 



