310 On Prophysaon, etc. 



times as long as the penis sac, which it enters at its apex. This sac is 

 cylindrical, stouter and longer than the vagina ; the retractor muscle is 

 Inserted opposite the entrance of the vas deferens, beyond which point 

 the sac is extended in a short delicate duct, which enters a large ovate 

 organ, one-third the length of the penis sac. This organ is the peculiar 

 characteristic of the species, present in all the six specimens examined. 

 It no doubt is of the same use as the bulb-lilie termination sometimes 

 found to the flagellum In other species, but is of extraordinary dimen- 

 sions. 



EXPLANATION OF PLATES XIII AND XIV. 



The separate organs of the anatomical figures will readily 

 be recognized, or may be compared with the figures in "Ter- 

 restrial Mollusks U. S.," I. 



Plate XIII. 



Fig. 1. Ariolimax niger. The extreme marginal teeth. 

 See p. 299, foot note. 



Fig. 2. ProjpJiysaon HemphillL The internal shell en- 

 larged. 



Fig. 3. The same. Digestive system. Same form as 

 fig. 5. 



Fig. 4. The same. The jaw greatly magnified. 



Fig. 5. The same. The genitalia of the form referred 

 to on p. 296. a, the genital bladder. 



Fig. 6. The same. The genitalia of the typical form, 

 still more enlarged. 



Fig. 7. The same. Central, lateral and marginal teeth 

 of the lingual membrane. 



Fig. 8. The same. External view of a specimen con- 

 tracted in spirits. Magnified. 



Plate XIV. 



Fig. 1. Helix Columbiana, Lea. The genitalia, a, the 

 genital bladder. 



Fig. 2. The same. Jaw. 



Fig. 3. Helix germana, Gld. The genitalia., a, the 

 genital bladder. 



