6 TEST ACE LLIDJE. 



Order I. STYLOMMATOPHORA. 



(Geophila, Ads. Nephropneusta,Ihering.) Eyes at the extremi- 

 ties of the superior tentacles. 

 Order II. BASOMMATOPHORA. 



(Branchiopneusta, Ihering.) Eyes at the bases of the tentacles. 



ORDER STYLOMMATOPHORA. 



Almost exclusively terrestrial mollusks, none fluviatile ; having 

 four tentacles, the superior pair the largest, invaginate or retrac- 

 tile, oculiferous at their extremities. 



Suborder I. MONOTREMATA. Oculiferous tentacles invertible; 

 male and female orifices united. Terrestrial. Shell usually 

 present and mostly external ; sometimes internal, or absent. 



Suborder II. DITREMATA. Oculiferous tentacles contractile, 

 not invertible ; male and female orifices widely separated. Ter- 

 restrial or aquatic. No shell. 



SUBORDER MO NO TEE MA TA. 



*Agnatha. Mouth without jaw. Carnivorous. 

 ** Gnathophora. Mouth with jaw. Phytophagous. 



*Agnatha. 



Radula generally without median teeth; lips often developed' 

 into feeler-like appendages, neck commonly elongated and pecu- 

 liarly furrowed on the back. 



Families. 



Testacellidae, Oleacinidse, Streptaxidse, Helicoidea. 

 See " Structural and S3^stematic Conchology, 5 ' iii, 11-18. 



FAMILY TESTACELLIDM. 



Animal slug-like, bearing a small ear-shaped shell near the 

 posterior extremity of the body. Lingual teeth long and 

 narrow, sharp-pointed, in oblique series. 



Synopsis of Genera. 

 Genus TESTACELLA, Cuvier, 1800. 



Animal limaciform, subcylindrical, tapering anteriorly ; ten- 

 tacles simple, mantle small, posterior, quite near the tail, covered 

 with a small external shell ; no longitudinal furrows above the 

 margin of the foot, and no caudal mucous pore ; no distinct 

 locomotive disk ; respiratory orifice at the posterior right edge 



