THE NATURAL HISTORY SURVEY. 105 
mens from Wolf Lake are generally small, rather thin and deli- 
cately and beautifully rayed. Specimens from Lisle, DuPage 
River are more compressed and higher in relation to length 
than are the specimens, generally, from other regions. The 
present species is frequently confounded with anodontoides, but 
is quite distinct from that species. 
Specimens collected July 25, 1896, contained embryos in 
the posterior third of the outer ctenidium measuring one-fifth 
of a mill. in diameter. The ctenidia at this time were much 
swollen and the embryos very numerous. The species in cap- 
tivity is remarkably active, ploughing its way through the sandy 
or muddy bottom with considerable speed. The writer has 
noticed that the excurrent siphon continually opens and closes, 
and at each closing a current of water filled with foetid matter is _ 
ejected. This operation is repeated on an average of twelve 
times in a minute. 
GROUP OF LAMPSILIS IRIS. 
33- Lampsilis iris Lea, pl. xiii., fig. 1; pl. xiv., fig. 2. 
Unio iris LEA, Trans. Amer. Phil. Soc., Vol. III., pp. 409, 411, 421, 439, 
pl. xi., fig. 18, 1829. 
Unio novi-eboract Lea, Trans. Amer. Phil. Soc., Vol. VI., pp. 127, 147, 
1838. Journ. Phil. Acad., Vol. IV., p. 47, pl. v., fig. 14, 1858. 
Shell: Rather small, stout, compressed, elliptical, rounded 
before, triangular behind in the male and broadly rounded in 
the female; dorsal margin nearly straight, ventral margin 
rounded; surface smooth and polished, marked by distinct lines 
of growth; umbones depressed, compressed, the apex directed 
anteriorly, dark reddish brown, marked by five elevated ridges 
which are more or less broken up into nodules; anterior um- 
bonal slope short and rounded; posterior slope long, flat, form- 
ing an obtuse angle; ligament long, narrow, stout, dark horn 
colored; epidermis yellowish or yellowish green, with numerous 
wide, interrupted dark green rays extending from the umbones 
to the ventral margin; cardinal teeth double in both valves, 
about equal in the left; the anterior teeth in the right valve very 
small, all elevated, triangular, serrated and striated; lateral 
teeth long, thin, lamellar, striated, almost straight; anterior ad- 
ductor muscle scar much longer than wide, deeply excavated, 
striated; posterior adductor muscle scar large, as wide as high, 
faintly marked, confluent; protractor pedis muscle scar wider than 
high, deeply impressed, striated; dorsal muscle scars situated 
in the cavity of the beaks, large, deeply excavated; pallial line 
