GASTEROPODA. 333 
each side of the back; mouth armed with horny jaws; stomach 
simple, liver compact. 
Distribution, 13 species. Norway and Britain. Under stones 
at low water,—25 fathoms. 7’. Hombergii, Cuvier, found on 
the scallop-banks, attains a length exceeding 6 inches. 
ScyLLzaza, L. 
Type, 8. pelagica, Pl. XITI., Fig. 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 branchiz 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. 
TEeTHyS, L. 
Etymology, tethys, the sea (personified). 
Synonym, Fimbria, Bohadsch. 
Type, T. fimbriata, L., Pl. XIII., Fig. 9. 
Animal elliptical, depressed ; head covered 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 
tength, 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 srnall dendritic 
gills are attached ;* foot very narrow. 
Distribution, 3 species. Straits of Sunda, on floating weed; 
Borneo, 
* This observation deserves further inquiry. 
