GASTEROPODA. 193 



SCYLL^A, L. 



Type, S. pelagica, PI. XIII. fig. 8. Etym. Scyllaea, a sea-nymph. 



Animal elongated, compressed; foot long, narrow and channelled, 

 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. 



Distr. Atlantic, S. Brit. Medit. On floating sea- weed. 



Nerea (punctata) Lesson, New Guinea; 10 lines long, with ear-shaped 

 tentacles, and 3 pairs of dorsal lobes. 



TETHYS, L. 



Etym. Tethys, the sea (personified.) Syn. Timbria, Bohadsch. 



Type, T. fimbriata, L. PL XIII. fig. 9. 



Animal elliptical, depressed; head covered by a broadly expanded, fringed 

 disk, with 2 conical tentacles, retractile into foliaceous sheaths ; gills slightly 

 branched, a single row down each side of the back ; reproductive orifices be- 

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



Distr. 1 sp. Medit. Attains a foot in length, and feeds on other mol- 

 luscs and crustaceans. (Cuvier.) 



? BORNELLA (Gray), A. Adams. 



Type, A. Adamsii, Gray. Lon. 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. 



Distr. 2 sp. Straits of Sunda, on floating weed ; Borneo, 



? DENDRONOTUS, A. and H.f 



Etym. Dendron, a tree, notos, the back. 



Type, D. arborescens, PL XIII. fig. 10. 



Animal elongated ; tentacles laminated ; front of the head with branched 

 appendages ; gills arborescent, in single series down each side of the back ; 

 foot narrow ; lingual teeth 10.1.10 ; stomach and liver ramified. 



Distr. Icy sea; Norway, Brit. On sea-weed and corallines; low-water 

 coralline zone. 



?DOTO, Oken. 



Etym. Doto, a sea-nymph. Ex. D. coronata, PL XIII. fig. 11* 



* This observation deserves further enquiry. 



f This and the following genera are placed by Alder and Hancock in the family 

 JEolidce ; they have a ramified stomach, but their external (zoological) characters 

 agree better with Tritonia than Molls. 



