6t 



PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



Tonkin — P. emigrans, MlldfE. ; one in the Abor Hills, Assam — 

 P. bahbagei, Gude ; one in the Loo-Choo Islands — P. Jiirasei, Pils. ; 

 all the others being natives of China. The armature is generally 

 less complicated than in the other members of the group ; in 

 P. schistoptychia, Mlldff., for instance, the parietal barrier consists 

 simply of strong vertical lamina, with a short support posteriorly 

 at its lower extremity and two similar supports anteriorly, one above 

 and one below ; while the palatal armature consists of eight small 

 denticles in two series of four each, a thin, horizontal fold above these 

 near the suture, with a minute denticle near its posterior termination 

 (see Fig. 3). In P. diptychia, Mlldff., on the other hand, the parietal 



Fig. 3. — Plectopylis schistoptychia. 



armature is coni]30sed of two strong vertical laminae, almost parallel 

 but slightly convergent above, the anterior one with a short support 

 anteriorly above, the posterior one crescent-shaped ; there are 

 six short more or less horizontal palatal folds (see Fig. 4). 





I 



L — Plectopylis diptychia. 



P. mMZ(^■s^^m, Mlldff., possesses one strong, lunate, transverse parietal 

 plate, on the anterior side of which are found a short, horizontal 

 fold above, next five minute denticles — the second and third being 

 united, forming a double one (see Fig. 5). The palatal folds are 



