GUDB : ON THE ARMATURE OF LAND MOLLUSCA. 



63 



parietal ridge at the aperture but free posteriorly ; a short distance 

 beyond it occurs a strong, vertical lamina with, posteriorly, a short 

 support below, and anteriorly a strong, horizontal fold, extending 

 a little over half the length of the median fold, while a third horizontal, 

 thin fold, close to the lower suture, commences just below the vertical 

 plate and is united with the parietal ridge at the aperture. Another 

 species in the same section, P. brahma, G-.-A,, has the palatal barriers 

 also in two series, but here the anterior set is composed of but four 

 rather short, horizontal folds, two above and two below, with 

 a considerable space separating the upper and lower folds ; while 



Fig. 2. — Plectopylis franqoisi. 



the posterior series exhibits no less than fourteen minute denticles 

 arranged in a transverse row slightly deflected anteriorly below. 

 P. cyclaspis, Bens., differs considerably in its armature from the 

 other members of the genus, the parietal barrier being trifurcate 

 with a free, short, horizontal fold below, while the palatal barriers 

 are five in number : the two upper short and horizontal, the third 

 crescent-shaped with the extremities curved downwards, the fourth 

 strong, broad, and vertical, intercalating with the two lower arms of 

 the parietal lamina, and below this another short horizontal fold. 

 The section Sinicola contains nineteen species, one being found in 



