Syxopsis Fresh-Water Mollusca 

 Subgenus CUMBERLANDIA Ortmann, 1912. 

 Shell as in the genus. 



41 



Fig. 142 



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

 tubes and with continuous septa, which run obliquely forwards. 



an 



Fig. 143 

 Type: Unio inonodonta Say, fig. 142. Animal, fig. 143. 



Family UNIONID.F:. 



■'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 water-tubes and distinct, interlamellar septa, running parallel to 

 the filaments. Alarsupium 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.) 



