160 



SYSTEMATIC ARRANGEMENT 



obliquely ; apex small, triangular, reflexed, denticulated on the edge ; 

 outer lateral teeth very numerous, hair-like, curved at the end (fig. 85) . 



Fig. 85. — Teeth of Gena elegans. 



5. Broderipia. 



Shell shield-shaped, oblong ovate, flattened ; apex posterior, sub- 

 involute, not spiral ; aperture very large, ovate, within iridescent, 

 pearly. Animal 1 Operculum ? 



1. B. rosea, Adams, Gen. Moll. t. 50. f. 3. 



Suborder II. Schismatobranchia, 



Gills in the form of two plumes on the left side of the gill- cavity, 

 one on each side of the slit on the mantle. Body and shell spiral. 

 Eyes peduncled. Sides of the foot tubercular, bearded above. Cen- 

 tral teeth large, very unequal, dissimilar (p. 136). 



Fam. VII. SCISSURELLIDvE. 



Fig. 86. — Animal of Scissit- 

 rella. 



Mantle-slit in front. Gills 1 Sides 



with very long slender beards. Tentacles 

 subulate, elongate, ciliated or serrated. 



Teeth 1 Foot narrow, truncate in 



front, tapering behind. Operculum horny. 

 Shell spiral ; whorls keeled, with a slit in 

 front of the keel, which is gradually filled 

 up as the shell enlarges. 



This family, though it contains only a 

 single recent genus, of small size, has many 

 fossil representatives of considerable size and 

 diversity of form. 



1. SCISSURELLA. 



Shell depressed, spiral, transparent, widely umbilicated; spire 

 short ; whorls keeled, with a narrow, subposterior slit at the end of 



