Synopsis Fresh-Water Moelusca 



67 



Marsupium occupying the basal half of the entire length of the outer 

 gills and having in front six to twenty beautiful folds; ovisacs distinct, each 

 ending below in an enlarged, rounded bulb, which has a colored spot in the 

 centre. 



mp 



Fig. 188 



Type: Uiiio f^hascoliis 1 lild., fig. 187. Animal, P. snbtcntus (Say), fig. 188. 



Genus OULIQUARIA Rafinesque, 1820. 



Shell inflated, solid, oval, ending in a tolerably sharp point behind, hav- 

 ing a row of large, compressed, longitudinal knobs running from the beaks 

 to the centre of the base, those of one valve alternating with the knobs of 

 the other, and a well developed posterior ridge, the space between the ridge 

 and the knobs somewhat excavated ; posterior slope and sometimes the en- 

 tire shell more or less corrugately sculptured ; beaks prominent, incurved 

 and pointed slightly forward toward a tolerably well developed lunule ; beak 

 sculpture strong, consisting of four or five heavy, parallel ridges, which fall 



Fig. 189 Fig. 190 



low in front, but are curved upwards behind ; epidermis smooth, generally 

 shining, painted with numerous, delicate, wavy, darker, broken rays; pseudo- 

 cardinals strong, distinct and ragged; laterals short, nearly straight; front 

 part of the shell verv solid, suddenly becoming rather thin, just behind the 

 knobs. Marsupium consisting of a few, distinctly marked ovisacs (4 to 7) 

 occupying a position just liehind the centre of the outer gills, projecting far 

 below the rest of the l)ranchire. their bases rounded. 

 Type: O. reilc.va Raf.. fig. 189. Animal, fig. 190. 



