Synopsis Frijsh-Water Moli^usca 

 Subgenus CUMBERLANDIA Ortmann, 1912. 



41 



Shell as in the s^enus. 



Fig-. 142 



.Animal as in the family, but having the gills with incomplete water- 

 tubes and with continuous septa, which run obHquely forwards. 



an 



b 



Fig- 143 

 T3^pe : Unio monodonfa Say, fig. 142. Animal, fig. 143. 



Family UNIONIDyE. 



"Diaphragm complete, formed by the gills; posteriorly the outer lamina 

 of the outer gill connected with the mantle to its posterior end; anterior 

 end of the inner gills separated from the palpi by a gap; branchial and anal 

 openings sharply separated from one another by the diaphragm; anal open- 

 ings very rarely not closed above and without supra-anal, generally closed 

 and with a supra-anal opening (which very rarely may be obliterated) ; 

 gills with v\^ater-tubes and distinct, interlamellar septa, running parallel to 

 the filaments. Marsupium in all four gills or only in the outer gills ; larva 

 a glochidium. Shell of very variable shape ; sculpture of the beak more or 

 less reduced, of various types, but originally of the concentric or zig-zag 

 pattern; hinge teeth perfect or imperfect; epidermis plain or with color- 

 markings." (Ortmann.) 



