PLECTOPYLIS. 73 



a. Shell not exceeding G mm. 



* One upper and one basal palatal fold. 



t A sliort ln)rizontal fold above parietal plate, blandn. 



tt Horizontal fold none minor. 



•** Only one basal palatal fold hanlvyi. 



,3. Shell" S-10 mm. 



* Parietal plate gives oft anteriorly a horizontal 



fold from npper extreniitj' ; one short hori- 

 zontal fold below lilectostoma. 



■■** No horizontal fold proceeding from parietal 



plate ; two short horizontal folds below . . affinis. 



II. Section Cheks^cia, Giuh. 

 (Second Section of Benson.) 



Sinistral or dextral. Umbilicus wide. Palatal folds horizontal or 

 oblique, sometimes with one oblique or vertical lamina. 



Type, P. leiojMs. 



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



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. ogJei. 



** Not connected ; shell l'4-26 mm nnder^oni. 



/3. Palatal folds^/^w; shell 11 mm serica. 



y. Palatal folds seven with two denticles laomontana. 



h. A free interrupted horizontal fold in front of 

 parietal plate ; palatal folds six, four inner 

 united by a vertical ridge, seven denticles 

 posteriorly ausfeni. 



B. Transverse parietal plate givin? off anteriorly above 



a short liorizontal fold, witli a denticle below plate. 



Palatal folds six ; shell 10-11 mm mnnipurensis. 



C. Transverse parietal plate giving off anteriorly ic/ozt- 



a lo7ig horizontal fold. 

 ti. With a median liorizontal fold contittuous to the 



peristome ; shell 20 mm bracliydisciis. 



h. With a median honzontal fold interrupted ; shell 



\() mm de.vtrorsa. 



2. Simstral. 

 A. Parietal plate simple. 



a. Horizontal fold below transverse parietal plate, 

 short. 



a. No median fold muspratti. 



fi. A long median fold present. 



* A third short horizontal fold between upper 



and lower paiietal folds, 

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

 tt Four palatal folds horizontal, two oblique ; 



shell 12 mm hengtungensis. 



