Synopsis Fresh-Water Mollusca 



33 



in front ; tentacles long, slender and pointed ; teeth of the radula multicus- 

 pid; central tooth with two basal denticles on each side. Verge small, 

 simple, lunate. 



Type: Melania altilis Lea, fig. 115. Radula, fig. 116. 



Subfamily LYOGYRINiE Pilsbry, 1916. 

 Shell minute, conical or subdepressed. Operculum circular, multispiral. 



Key to the genera of Lyogyrincc. 



Shell amnicoliform Lyogynts. 



Shell valvataeform (s. g-) Haiiffenia. 



Genus LYOGYRUS Gill, 1863. 



Shell very small, spiral, dextral, smooth, umbilicate ; globose- 



turbinate or elongate-ovate ; aperture nearly circular ; peritreme 



continuous, frequently quite separated from the body-whorl. 



Operculum corneous, circular, multispiral. 



Rostrum bilobed in front, half as long as the tentacles, which are rather 



stout ; foot auriculated in front ; gill external. Dentition as in Palndestrina, 



basal denticles on rachidian tooth two on each side. 



Fig. 117 



Type: Valvata pupoidca Gld., fig. 117. 



Genus HORATIA Bourguignat, 1887. 

 Shell very small, amnicoliform, thick-shelled, umbilicate, almost smooth; 

 whorls only 3-4, convex, rapidly increasing, the last large, rounded ; suture 

 impressed; aperture very oblique, rounded; lip adherent, straight, sharp; 

 columella thickened, incurved. Operculum corneous, 

 transparent, purple-red, with 3-4 slowly increasing spi- 

 rals and an almost central nucleus. 



Type: (first species) Horatia klecakiana Bgt. 



Subgenus HAUFFENIA Pollonera, 1898. 



Shell minute, rather thin, valvatseform, widely 

 umbilicate. 



Type: (first species) Horatia tellini Poll. 

 Example: Horatia micra (P. and F.), fig. 118. 



