FAMILY 1. LIMACINEA. 63 
cavity, the posterior extremity of the animal is enclosed within a small 
spiral heliciform shell, into which it can only partially retire. De Férus- 
sac regarded the Vitrine as being much more closely allied to the Coli- 
macea than to the Limacinea ; for in his grand distribution of the land and 
freshwater mollusks, he refers them to that family as forming two sub- 
genera of Helices, under the new titles of Helicolimax and Helicarion, the 
varieties represented in our Plate. 
The Helix citrina (subgenus Helicella, De Férussac) and its cognate 
species, which have been separated by Gray for the formation of his 
genus Nanina, are united by Quoy and Gaimard to the Vitrine ; there is 
undoubtedly a strong affinity between them, but still we cannot subscribe 
to the union in one and the same genus of two mollusks, whose shells 
differ so entirely in their structure and composition. 
The shell of Vitrina may be described as being rotundately ovate, some- 
what heliciform, thin, fragile, rather depressed, covered with a green shi- 
ning epidermis, and simply convoluted over the posterior extremity of 
the animal ; the spire is short, and the aperture very large, semilunar, and 
wider than it is long; the margin is simple, and the columella linear. 
Examples. 
Pl. CLXIE. *Fig, 1. 
VirRINA PELLUCIDA, Draparnaud, Hist. des Moll. Terr. et Fluv., p. 119. 
pl. 8. f. 34 to 37. 
Hele pellucida, Muller. 
Helicolimaz pellucida, De Férussac. 
Pl. CLXII. Fig. 2. 
Virrina Cuvier, Sowerby, Genera of Shells, No. 11. 
Helicarion Cuvierii, De Férussac. 
