822 _ QUADRULA 
Unio pilsbryt Marsu, Nautilus, V, 1891, p. 1.—Prispry, Pr. 
Ac. N. Sci. Phila. 1892, p. 131, pl. vit, figs. 7, 8; Nautilus, 
VIL 18093" plaseehes ge: 
Quadrula undulata var. pilsbryt SIMPSON, Syn., 1900, p. 760. 
I do not think this 1s more than a variety of wndulata. It is 
more wedge-shaped when viewed from above, has a browner 
epidermis than the ordinary manifestation of that species, and 
the plications are somewhat broken into nodules, a character 
often found in wndulata. 
On the one hand this species closely approaches Q. plicata 
and on the other it almost connects with forms of Q. heros. 
Ordinarily it is much more compressed, is shorter and has 
lower and less inflated beaks than the former, but there is a 
great deal of intermediate material. Frequently the strong, 
oblique folds become broken up by cross folds until the sculp- 
ture so closely resembles that of heros that the two forms can 
scarcely be separated. The Unio pilsbryi of Marsh shows 
something of this style of sculpture. 
A peculiar shell belonging to Mr. J. H. Ferriss, of Joliet, 
Illinois, from Iake Winnipeg, has been examined by the writ- 
er. It has unusually strong growth lines and is quite full in 
the ventral region, and has only the very faintest vestiges of 
plications below the lower part of the posterior ridge. I re- 
gard it as a smooth form of Q. undulata, and if any consid- 
erable number of such specimens were found it might be 
worthy of a varietal name. 
QuapruLA picITATA. (Morelet). 
Shell large, very solid, subcompressed, irregularly elliptical 
or subrhomboid ; beaks moderately developed ; dorsal line near- 
ly straight; anterior end rounded and cut away somewhat be- 
low; base line nearly straight; posterior end rounded, some- 
what pointed about on the median line, angular above; surface 
strongly, concentrically striate, and nearly covered with strong 
folds, which radiate from behind the beaks to a point some- 
what lower on the disk and extend to the border of the shell ; 
anterior end having low, rather regularly arranged pustules ; 
