MANUAL OF NATURAL HISTORY. 1 37 



a lateral fringe ; head-lobes developed ; shell 

 turbinate, pearly within ; operculum calca- 

 reous. 



2. FAMILY. Top-Shells (Trochidse). Foot with a 



lateral fringe ; head-lobes rudimentary ; shell 

 conical, spiral, pearly within; operculum 

 horny. 



3. FAMILY. False-Ears (Stomatellidse). Foot with 



a lateral fringe ; front edge of mantle entire ; 

 muscular impression crescentic ; shell ear- 

 shaped, imperforate, pearly within ; opercu- 

 lum none or rudimentary. 



4. FAMILY. Sea-Ears (Haliotidge). Foot with a 



lateral fringe ; head-lobes developed ; mantle 

 with the front edge fissured ; muscle of at- 

 tachment oval, central; shell ear -shaped, 

 pearly within, with a series of holes ; oper- 

 culum none. 



5. FAMILY. Nerites (Neritidae). Foot simple, with- 



out a lateral fringe ; head-lobes none ; shell 

 spiral, turbinate, not pearly within; oper- 

 culum sub-spiral, calcareous, with an internal 

 process. 



II. SUB-ORDER. SESSILE-EYED SCUTIBRANCHS 

 (Edriophthalmata). 



Eyes sessile, or on a slightly-raised tubercle on 

 outer side of base of tentacles ; shell (adult) symme- 

 trical, conical, not spiral, not pearly within ; oper- 

 culum none. 



