VITRINA. 53 



very many of the islands of both the Atlantic and the 

 Pacific. 



REMARKS. This genus, as before observed, is a con- 

 necting link between the Limacidce and the present 

 family. In addition to the anterior part of the mantle, 

 which, as in that family, lies upon the back and extends 

 to the head, there are one or more processes or prolon- 

 gations of its margin, narrow and somewhat tongue- 

 shaped, which are given off from its anterior and pos- 

 terior parts, and reflected back over the shell, the peri- 

 ostraca of which they protect from the adhesion of 

 foreign matter, and retain in a smooth and polished con- 

 dition. The respiratory orifice is in the mantle, on the 

 right side, but posterior to its position in the Limaces. 

 The tentacles are short compared with those of Helix, 

 and the inferior pair especially so. The upper surface 

 is covered with minute glandular granulations and fur- 

 rows, and moistened with a limpid mucus. It is asserted 

 by many authors, that the animal can withdraw itself 

 only partially into its shell ; but this must be an error, 

 for M. Nilsson declares most positively of Vitrina pellu- 

 cida, and Mr. Lowe* of Vitrina lamarckii, that the 

 shell can contain the entire body. Its aspect when in 

 motion is that of a Limax bearing the shell of a Helix 

 upon its back. 



The genus is one preferring a low temperature, occu- 

 pying, in Europe, the northern countries, and when found 



* Zoological Journal, iv. p. 338. 



