ORTMANN: monograph of the naiades of PENNSYLVANIA. 271 



EuRYNiA (Eurynia) nasuta (Say) (1817).^'^ 

 Lampsilis nasuta (Say) Simpson, 1914, p. 97. 



Plate XVI, figs. 10, 11. 

 Records from Pennsylvania: 



Say, 1817 (Delaware and Schuylkill Ri\-ers). 



Gabb, 1861 (Schuylkill River and League Island, Philadelphia; " Little Perkiomen Creek ")■'" 



Hartman & Michener, 1874 (Schuylkill River, Chester Co.)- 



Marshall, 1895 (Philadelphia). 



Schick, 1895 (Delaware and Schuylkill Rivers, Philadelphia). 



Ortmann, 19096, p. 202, 205. 



Characters of the shell: Shell of medium size and medium thickness. Outline 

 subelliptical or sublanceolate, elongated, distinctly over twice as long as high. 

 Anterior margin rounded. Lower margin more or less curved. Upper margin 

 straight or gently curved, forming (at least when young) a distinct angle with the 

 posterior margin, which slopes down obliquely, joining the lower margin in a dis- 

 tinct, but rounded, posterior angle or point. Thus the shell is distinctly attenuated 

 and pointed behind, although the point itself is narrowlj^ rounded. Beaks low, 

 hardly elevated above the hinge-line. Beak-sculpture (Marshall, 1890, fig. 5) 

 consisting of five to seven fine bars, the first one or two subconcentric, the following 

 double-looped, with a distinct re-entering angle or sinus back of the middle. An- 

 terior loop broadly rounded, posterior loop narrow, somewhat angular upon the 

 posterior ridge, and indistinct upon the posterior slope. Valves moderately 

 convex, flattened upon the sides. A posterior ridge is present; it is most distinct 

 near the beaks, and angular, farther downwards it becomes broader, is more 

 roimded and indistinct. Posterior slope slightly concave near the beaks, becoming 

 flatter or even somewhat convex toward the posterior end of the shell. In young 

 sheUs it is compressed and elevated toward the posterior angle of the upper margin. 



Epidermis dark olive-green or brown, with or without rays. The latter are 

 poorly developed, dark green, straight, narrow or somewhat wider, and generally 

 visible only (if at aU) in the posterior section of the shell, just in front of the pos- 

 terior ridge, and upon the posterior slope. In younger specimens the rays may 

 extend over the whole surface. In other cases, they are entirely absent. Some- 

 times there are concentric light and dark bands, the latter marking the growth- 

 rests. 



"« Not 1816. 



'" Perkiomen Creek is a tributary of the Schuj'Ikill in Montgomery County. There is no " Little 

 Perkiomen Creek " to my knowledge. 



