14 



LAND AND FRESH-WATER SHELLS OF N. A 

 Fig. 2. 



[part l 



Lingual dentition of Olandina truncata 



curved, thorn-like teeth ; cen- 

 trals* long, slender, straight, 

 widened at base. 



Subgenus GLANDINA, s. str. 

 Shell ovate, or ovate-oblong, 

 plicately-striate, generally of a 

 silken lustre, but never glitter- 

 ing, and usually decussated with 

 delicate revolving lines ; suture 

 crenulated ; aperture equalling 

 about half the shell's length, its 

 peristome simple. 

 Fig. 3. 



Glandina truncata, one-half the natural size. 



Body elongated, narrowed anteriorly ; eye-peduncles long, 

 having the eye spots on the posterior face, behind the tips, which 

 are deflected ; tentacles half the length of the eye-peduncles, 

 bulbous, and somewhat deflected at tip ; on each side of the oral 

 aperture is a retractile, palpiform appendage, attenuated at tip, 

 and more or less recurved, nearly as long as the eye-peduncle, 

 the bases separated by a fissure in front ; buccal pouch capable 

 of a proboscidiform protrusion, the aperture furnished with three 



' Albers and Martens describe the lingual membrane as having no 

 central line of teeth, and it is so figured by Leidy in the Terrestrial Mol- 

 lusks (11, 303). Morse has detected a central line as figured above. In 

 comparing the lingual membrane with that of the Helicidce it may be said 

 that the lateral teeth are entirely omitted, tlie uncini alone being present: 

 in Zomtes the uncini are equally prominent, and the laterals very few ; in 

 J^Iacrocyclis, also, no laterals are present. 



