VITRINA. 55 



more valid than one founded upon the absence of so 

 important organs as the lower pair of tentacles, a de- 

 parture from the structural type of the family, which 

 is always accompanied by the modification and adapta- 

 tion of some other organ to perform their usual functions. 



The general structure of the animal is like Helix, and 

 as in that genus, as well as in Limax, there are species 

 which possess a terminal mucus pore like Arion. To 

 these M. Ferussac gave the name of Helix-arion, while 

 he retained the name of Helico-limax for those which, 

 like the true Limax, are destitute of the terminal sinus 

 or pore. 



The species hitherto discovered are few, and do not 

 appear to be so prolific as the other genera, hence they 

 are not numerous in individuals. 



1. VITRINA PELLUCID A, MULLER. 

 PLATE LXVII. a. FIGURE!. 



V. testa sub-depressa, tenuissima, hyalina, nitida, imper- 

 forata; anfractibus tribus convexiusculis ; apertura sub-ovata, 

 obliquissima ; peristomate simplici. 



SYNONYMS AND REFERENCES. 



I'i/rinapcllucida, SAY, Expecl. St. Peters. II. p. 258. 

 ADAMS, Shells of Vermont, p. 12. 



DESCRIPTION. 



ANIMAL. Whitish, grayish, or blackish, large coin- 

 pared with the shell. Head, tentacles, and eyes black ; 

 inferior tentacles very short. The prolongation of the 



