54 



Bryant Walker 



dermis shining, often rayed ; a single imperfect tooth in each valve and 

 sometimes vestiges of laterals ; nacre purplish shading to blue at the edge ; 

 pallial line radially ridged. 



Animal having the foot very large, as long as the shell when extended, 

 of a subcylindrical, compressed shape, with a distal swelling. The middle 

 portion of the outer gills only marsupial. Glochidia semicircular, slightly 

 oblique, inequivalve, without points or hooks. 



Type: Anodonta (L.astcna) lata Raf., fig. i66. 



Genus GONIDEA Conrad, 1857. 



Shell elongated, subtriangular, much narrowed in front, wide behind, 

 inflated, subsolid, usually with a high, sharp posterior ridge; beaks rather 

 sharp but not high, the sculpture consisting of a few, strong, concentric 

 bars: epidermis rayless ; hinge with a rudimentary pseudocardiital and lat- 

 eral in each valve, though these are sometimes wanting; pallial line with a 

 trace of a sinus hehind; nacre lurid to purplish. 



Fig. 167 



Female having all four gills marsupial; with well developed septa, run- 

 ning parallel to the gill filaments and forming w^ater tubes ; septa not all con- 

 tinuous, but are often interupted, chiefly so toward the proximal (basal) 

 part of the gill and, towards the edge, frequently shorter septa are inter- 

 calated. Glochidia subovate or nea-rly subcircidar, without hooks. 



Type: Anodonta aiigiilafa Tea, fig. 167. 



Subfamily ANODONTIN.T: Ortmann, 1912. 



'Tnner lamina of inner gill free from the abdominal sac, or more or less 

 connected with it, rarely entirely connected ; supra-anal opening well sep- 

 arated from the anal, sometimes the connection of the mantle separating it 

 from the anal is very long and the supra-anal is quite short ; branchial open- 

 ing well defined, no papillae or flaps in front of it on the edge of the mantle ; 

 marsupium formed by the outer gills in their length, distending, when 



