PLEUROBRANCHID.E. 



107 



Ancula (Loven). Slender, lengthened; mantle 

 entirely adhering, its margin adorned with club- 

 shaped filaments ; tentacles club-shaped, laminated, 

 with filaments on their stems. 



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



TRIBE II. TECTIBRANCHIATA. 



Shell (where present) enclosed within the flesh. 



Shell a thin convex shield : 



Gill between the edge of the 



mantle and the foot .... 



Gill in the back, beneath the 



shell 



Shell globose or cylindrical, rolled Bullada. 

 Shell external Tornatellada. 



150 



FAMILY I. PLEUROBRANCHID^E. 



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. 



