GUDE : ON THE ARMATURE OF LAND MOLLUSCA. 



65 



six in number, more or less horizontal, with a little elongated denticle 

 posteriorly between the fifth and sixth. 



Fig. 5. — Plectopylis muUispira. 



Genus Sagda, Beck. 



This is restricted to Jamaica, except the subgenus Odontosagda, 

 Mts., which occurs in Haiti and Cuba. The armature, generally- 

 visible through the shell-wall, is in the form of revolving, internal 

 laminae or interrupted laminae forming series of denticles ; in the 

 section of Hyalosagda, Mts., they are, however, absent. 

 S. cookiana, G-m., exhibits this interrupted lamina on the basal wall, 

 and has, in addition, a short columellar fold. 



In S. alveare, Pfr., the basal lamina is strongly developed and 

 continues over the whole of the last whorl ; the coluniellar fold is 

 also well developed in some specimens. In S. spiculosa, Shutt., the 

 basal lamina is very long, extending beyond the last whorl, but in 

 S. triptycha, Shutt., it is only about one-third of a whorl long, 

 although the foundation of the previous lamina can be observed 

 through the shell-wall for a considerable length ; the columellar 

 fold is here in the form of a strong transverse nodule. 



Genus Pleurodonta, Fischer de Waldheim. 



A large genus divided into several subgenera, or sections, 

 distributed over the West Indies and northern South America. 

 Many species are provided with teeth at the aperture. The Jamaican 

 P. hainbridgei, Pfr., and P. acuta, Lam., with its numerous varieties, 

 exhibit one or two teeth on the basal margin of the peristome, 

 becoming more strongly developed and entering in P. lucerna, Mlill. 

 In P. soror, Fer., and P. peracutissima, C. B. Ad., also from Jamaica, 

 the mouth is much contracted, and the basal margin bears four strong, 

 elevated, entering teeth nearly closing the aperture ; behind the 

 basal margin of the peristome occur corresponding scrobiculations. 

 Most of the other forms of the section Pleurodonta, s.s., which is 

 restricted to Jamaica, possess variants of his form of armature. 



The section Caprinus, Montfort, distributed over the Lesser 

 Antilles, possesses some remarkable forms, P. nuxdenticulata, 



