208 MEMOIRS OF THE CARNEGIE MUSEUM. 



Ellipsaria fasciolaris (Rafinesque) (1820). 

 Ptychobranchus phaseolus (Hildreth) Simpson, 1941, p. 333; Ellipsaria fasciolaris 

 (Rafinesque) Frierson, 1914a, p. 7; Ptychobranchus fasciolaris (Rafinesque) 

 Vanatta, 1915, p. 554. 



Plate XIII, figs. 1, 2, 3. 

 Records from Pennsylvania: 



Harn, 1891 (western Pennsylvania). 

 Marshall, 1895 (Allegheny Eiver, Warren Co.). 

 Rhoads, 1899 (Beaver River, Wampum, Lawrence Co.). 

 Ortmann, 19096, pp. 194 and 202. 



Characters of the shell: Shell of medium size, but comparatively thick and 

 heavy. Outline subelliptical, more or less elongated; when old, often humped 

 (sub triangular) , and drawn out at the lower posterior end. Upper and lower 

 margins more or less convex, posterior end narrower than anterior, rounded or 

 bluntly pointed. In old specimens the lower margin may be straight, and it 

 sometimes becomes even concave in the middle. Beaks in front of the middle, 

 very little elevated above the hinge-line. Beak-sculpture rudimentary, consisting 

 of two or three faint ridges which are interrupted, and have thus a tendency to 

 appear double-looped. 



Valves moderately and rather evenly convex, slightly more flattened on the 

 sides. Posterior ridge practically absent, or indicated only by a stronger con- 

 vexity of the valves. No sculpture upon the surface. 



Epidermis yellowish to light brown, rarely dark brown; generally ornamented 

 with dark green rays, which are most distinct in young specimens. The rays are 

 capillary and interrupted, but are generally grouped together in bundles, and 

 very often fused together, so as to form more or less squarish, green spots. There 

 is great variability in the size and the arrangement of these spots, and in very 

 rare cases they are entirely missing. Old shells have the rays less distinct, and 

 the epidermis becomes more or less uniformly brown. Concentric bands of color 

 are absent, or the color is only slightly darker along the gi'owth-lines. 



Hinge well-developed. Pseudocardinals stumpy, heavy, but not much ele- 

 vated. Laterals thick and heavy, club-shaped, thicker posteriorly. Interdentum 

 narrow. Beak-cavity shallow. Dorsal muscle-scars in the beak-cavity. Ad- 

 ductor-scars distinct and rather deep. 



Nacre white, generally without any color, except in very young specimens, 

 where there may be a faint pink blush. 



Externally there are no sexual differences in the shell, except that the males 



