PLECTOPYLIS. 73 



a. Shell not exceeding- 6 mm. 



* One upper and one basal palatal fold. 



t A short horizontal fold above parietal plate, blanda. 



ft Horizontal fold none minor. 



** Only one basal palatal fold hanleyi. 



13. Shell 8-10 mm. 



* Parietal plate gives off anteriorly a horizontal 



fold from upper extremity ; one short hori- 

 zontal fold below plectostoma. 



** No horizontal fold proceeding from parietal 



plate ; two short horizontal folds below . . affinis. 



II. Section CHERSJECIA, Gude. 

 (Second Section of Benson.) 



Sinistral or dextral. Umbilicus wide. Palatal folds horizontal or 

 oblique, sometimes with one oblique or vertical lamina. 



TYPE, P. leiophis. 



Range. From Assam through Upper Burma and Laos to Tenasserini. 



1. Dextral. 



A. Transverse parietal plate simple. 



a. Free horizontal parietal folds none. 

 a. Palatal folds six. 



* Connected by a transverse ridge ; shell 27 mm. oglei. 



** Not connected ; shell 24-26 mm. . . * andersoni. 



j8. Palatal folds Jive ; shell 11 mm serica. 



y. Palatal folds seven with two denticles laomontana. 



b. A free interrupted horizontal fold in front of 



parietal plate ; palatal folds six, four inner 

 united by a vertical ridge, seven denticles 

 posteriorly austeni. 



B. Transverse parietal plate giving oft' anteriorly above 



a short horizontal fold, with a denticle below plate. 



Palatal folds siv ; shell 10-11 mm munipurensis. 



C. Transverse parietal plate giving off anteriorly below 



a long horizontal fold. 

 . With a median horizontal fold continuous to the 



peristome ; shell 20 mm brachydiscus. 



b. With a median horizontal fold interrupted ; shell 



16 mm dextrorsa. 



2. Simstral. 

 A. Parietal plate simple. 



a. Horizontal fold below transverse parietal plate, 

 short. 



a. No median fold muspratti. 



/3. A long median fold present. 



* A third short horizontal fold between upper 



and lower parietal folds. 



t Palatal folds all horizontal ; shell 10 mm.. . perarcta. 

 tt Four palatal folds horizontal, two oblique ; 



shell 12 mm kenytungensis. 



