EXPLANATION OF PLATE XXI. 
Trochomorpha helicinoides , H. & J., magnified. 
Fig. 1. Dead animal extruding from the shell. 
,, 2. Genital system. 
„ 3. Portion of radula, showing central, transitional and margina. 
teeth. 
,, 4. Jaw. 
[From drawings by the Author.] 
