404 Journal of the Asiatic Society of Bengal. [N.S., XIX, 
denticulations. Gill-filaments Jong, extending almost all the 
way across the roof of the branchial chamber. Male intro- 
mittent organ absent (? always). 
Type-genus. Delavaya Heude. 
Geographical and palaeontological range. The lakes ot 
Yunnan and possibly Cambodia; also the tertiary lake-beds 
of the Northern Shan States of Burma. 
Key to the Genera of Delavavidae. 
1 Shell trochiform s 
2. Shell turrited, conical or conoidal. 
A. Shell smooth, conoidal. Lateral 
teeth of radula without sub- 
sidiary denticulations .. Delavaya. 
B. Shell with a spiral ridge or 
Fenowilia. 
ridges. ne ~~ 
I. Shell with a single smooth 
peripheral ridge. Latera 
teeth of radula with lateral 
denticulations .. Parapyrgula. 
ll. Shell with more than one 
tuberculate spiral ridge .. Paraprososthenia. 
in the male. In this last character, and also to some extent in 
the structure of the radular teeth, the family approaches the 
North American Pleuroceratidae, in which Dr. Baini Prashad 
and I included three of the genera provisionally in 1919. 
Genus Delavaya Heude. 
1889. Delavaya, Heude, Journ. Conchyliol., XX XVIII, p. 46. 
Delavaya rupicola Heude. 
1890 Delavaya rupicola, Hende, Mém. Hist, Nat. Emp. Chinois, 1. 
ane Pie 172, Plate XXXIIT, Figs. 8-9, 10 and 10a. 
: ero rupicola, Annandale and Prashad, Rec. Ind. Mus., XVI, 
pcre a Se ames i ean Ss 
