102 



GASTROPODA. 



Family III. Tritoniad^. 



Gills simple or arborescent, arranged along the 

 sides of the back ; tentacles retractile into sheaths ; 

 tongue with one central, and numerous lateral 

 teeth in each row. 



Tritonia (Cuv.). Body lengthened, thick ; ten- 

 tacles two, branching; head with a warted or 

 fringed veil ; gills branching in a single row, on a 

 ridge on each side. 



T. Hombergi. 



lineata. Fig. 138 ; f . 



T. alba, 

 plebeia. 



136 



137 



138 



Scyllma (Linn.). Body compressed; foot long, 

 narrow, grooved ; back with two pairs of lateral, 

 wing-like lobes, bearing small tufted gills on their 

 inner surfaces ; tentacles two, with fringed tips ; 

 oceanic. 



S. pelagica. Fig. 139 ; f . 



Dendronotus (Alder and Hancock). Tentacles 

 fringed with membranous expansions {lamince) ; 



