76 THE NAUTILUS. 



Plagiola elegans (Lea). 



Anodonta imbecilis (Say). The species suborbiculata which 

 might be expected here was not found. Undoubtedly it will be 

 found in the adjacent swamp ponds. 



Anodonta grandis leonensis (Lea). 



Anodonta texasensis (Lea). 



Arcidens confragosa (Say). 



Uniomerus tetralasmus (Say). 



Crenodonta perplicata (Con.). 



Crenodonta trapezoides (Lea). 



Quadrula (TritogonioC) tubercidata (Bar.). 



Qvadrula pustulosa (Lea). 



FUSCONAIA SELECTA n. sp. Plate IV. 



Shell large, solid, quadrate to rhomboidal, much inflated, and 

 inequilateral; dorsal margin evenly curved, gradually curving 

 into the anterior and posterior margins; anterior margin some- 

 what projecting but regularly rounded; posterior margin obli- 

 quely curved, meeting the basal margin in a blunt, rounded 

 point on the base line; basal margin nearly straight, slightly in- 

 curved in front of the posterior ridge; umbonal region greatly 

 inflated, flattened in the centre, the greatest diameter of the shell 

 being through the anterior portion; beaks prominent, incurved, 

 their sculpture indeterminate by reason of erosion; posterior 

 ridge strong, roundly angled, extending to posterior point; a 

 shallow medial depression extends from the beaks to the basal 

 emargination, in front of the posterior ridge: the central portion 

 of the disk is decidedly flattened; the posterior area is wide, flat- 

 tened toward the margin, and markedly incurved from the pos- 

 terior ridge; surface smooth, with regular and even growth-lines, 

 having the rest-periods clearly defined; epidermis polished and 

 shining in young and half-grown shells, rougher in mature spec- 

 imens; colored bright reddish-brown, with an undercast of yel- 

 low or ochre or occasionally green, becoming with age dull red- 

 brown, deeping to black on the umbonal region; young shells are 

 faintly and beautifully rayed; in young shells the epidermis is 

 " faintly, radiately puckered or festooned, giving an appearance 

 of superficial, radiating stria3" extending from beaks to basal 

 margin, and these are stronger on the dorsal area immediately 



