ORTMANN: monograph of the naiades of PENNSYLVANIA. 63 



part of the shell, and may be scarce or nearly absent upon the posterior slope. 

 Tubercles variable in size, shape, and arrangement. There is no definite arrange- 

 ment, except sometimes a concentric one, parallel to the growth-lines. The shape 

 of the tubercles may be rounded or tear-like, but generally there are at least some, 

 which are peculiarly compressed and transversely elongated (appearing as "pinched 

 up"). The transverse dilatation of the tubercles is not verj^ great. The tubercles 

 may be rather crowded and numerous, or they may be scarce, sometimes only a 

 few are developed, and they often disappear entirely toward the lower margin. 

 Posteriorly, upon the posterior slope, the tubercles maj^ be missing, or a few, or 

 they may be as numerous as in the middle of the shell, or may even assume the 

 shape of nodular, radiating ribs. 



Epidermis yellowish brown to rusty or chestnut-brown, rather dark, when old. 

 Very often the posterior slope is lighter than the rest, yellowish or olive-browTi. 

 Growth-rests darker. Greenish, indistinct rays are very rarely indicated and only 

 in young specimens. 



Hinge-teeth well-developed. Pseudocardinals divergent, ragged. Interden- 

 tum moderately wide. Lateral teeth moderately long, strong. Beak-cavity 

 moderately deep. Dorsal muscle-scars on the hinge-plate. Nacre whitish, often 

 suffused with a delicate pink inside of the mantle-line, most intense toward the 

 hinge-teeth. Very rarely the whole interior is pink. 



No sexual difference whatever in the shells. Call's remarks (1900, p. 485) 

 about the differences of the males and females do not at all hold good. 



L. H. D. 



Size: 1. Industry, Cat. No. 61.3882 90 mm. 78 mm. 46 mm. 



2. Sliippingport, Cat. No. 61.3881 69 " 61 " 38 " 



3. St. Marys, Cat. No. 61.4595 69 " 71 " 41 " 



Soft parts (See Ortmann, 1912, p. 361). Breeding season: Gravid females and 

 glochidia have not yet been observed. On June 20 to 22, 1911, I obtained a good 

 number (about fifty) specimens in the Ohio at St. Marys; additional ones were 

 found on July 13, 1911, at Portland. All had the characteristic light orange color 

 of the soft parts. Of about two dozen females none was gravid, and every one had 

 only the outer gills marsupial. The sexual glands were grayish or brown and in 

 many cases distinctly pinkish. Thus it is probable, that the eggs also are pink, 

 as in P. cyphyus. 



Remarks: Externally in shape and sculpture this species greatly resembles 

 Quadrida pustulosa (Lea) and Rotundaria tuberculata (Rafinesque) . In the tubercles 

 the resemblance to the latter species is so great that there might be a close genetic 



