PLEUROBRANCHID^. 



107 



Ancula (Loven). Slender, lengtliened ; mantle 

 entirely adhering, its margin adorned witli club- 

 shaped filaments ; tentacles club-shaped, laminated, 

 with filaments on their stems. 



A. cristata. Fig. 150 ; n. s. 



Tribe II. Tectibeanchiata. 



Shell (where present) enclosed within the flesh. 



Shell a thin convex shield : 



Gill between the edge of the 

 mantle and the foot .... Fleurobranchida. 

 GiU in the back, beneath the 



shell Aplt/siada. 



SheU globose or cylindrical, rolled BuUadae. 

 Shell external Tornatellad<B. 



149 



cM-. 



150 



151 



Family I. Pleurobranchid^. 



Shell wanting, or concealed within the substance 

 of the mantle, protecting the intestines ; gills 

 feather-shaped, situated in the angle formed by the 

 mantle and the foot. Food vegetable. 



