GASTROPODA 



497 



R. gouldi (Couthouy) (Fig-. 756). Shell white and shining, with a 

 yellow periostiacum; spire conical; 7.5 mm. long-; 2.5 nnu. wide: Maine 

 to Cape Hat (eras. 



2. ToRNATiNA Adams. Shell with an elevated apex; inner lip with 

 fold; suture channeled: 50 species. 



T. canaliculata (Say). Shell with a low spire, pol- 

 ished, with a channeled suture, white without spots ; length 

 5 mm. ; width 2.5 mm. : Atlantic coast south of Cape Cod, 

 in shallow water. 



Family 3. SCAPHANDRIDAE. 



Fig. 756 



Retusa gouldi 



(Dall). 



Shell external, ovate, spire sunken ; aperture narrowed 

 above; inner lip spirally convoluted; outer lip acute; 

 head broad and short; epipodia usually well developed; head quadran- 

 gular, with eyes at base of tentacular lobes: 6 genera. 



1. DiAPHANA Brown. Shell thin and transparent; both inner and 

 outer lips sinuous; epipodia wanting: species few. 



D. debilis (Gould). Shell small, greenish-white, with 4 whorls, all 

 rising to the same height, partially umbilicated; 3.5 mm. long; 2.5 mm. 

 wide: Atlantic coast south to New Jersey, in 6 to 50 fathoms; Europe. 



2. Cylichnella Gabb. Tentacle lobes united and indistinct, with 



eyes on their front base; shell solid, without spire: 

 40 species, mostly in deep water. 



C. oryza (Totten) (Fig. 757). Shell white, 

 ovate; length 7 mm.; width 2.5 mm.: Maine to 

 Connecticut. 



Fig. 757 Fig. 758 



Fig. 757— Cylichnel- 

 la oryza (Verrill). 

 Fig. 7.58 — Haminea 

 soUtaria (Dall). 



Family 4. AKERIDAE. 



Shell external, fragile, light-colored, usually 

 covered by the large epipodia, cylindrical or ovate, 

 with a very small sunken spire and a large aperture with a sharp outer 

 lip: 5 genera and 70 species. 



Haminea Leach. Shell unicolored, green, or yellow, thin and horny. 

 H. solitaria (Say) (Fig. 758). Shell ovate, 9 mm. long and 6 mm. 

 wide, shining, with deep, microscopic, impressed lines : common along the 

 Atlantic coast from Massachusetts Bay to South Carolina. 



Family 5. PHILINIDAE. 



Shell internal, sometimes absent, convex, with a large aperture; 

 epipodia large and fleshy, folded over the back; head without tentacular 

 processes: 4 genera. 



