1889.] Zoology. 641 
myself discovered several specimens of this species in Cayuga Lake 
Inlet, five of which we captured. 
One year ago Professor F. Star informed me that they were seen by 
him in the spring, in large numbers, in the small streams tributary to 
the Cedar River, Iowa. 
This spring I collected about sixty specimens in a small brook from 
two to five feet wide, near Cedar Rapids, and many others were seen, 
all in a distance of about three-fourths of a mile. 
In 1886 we compared the five specimens from Cayuga Lake Inlet 
with as many more specimens from Indiana, noting only this 
difference : in the Inlet specimens the extreme mandibulary cusps were 
larger than the inner ones, while in the specimens from Indiana all 
the cusps were subequal. 
Dr. B. G. Wilder has kindly sent me twenty specimens from Ithaca, 
N. Y. These I have carefully compared with the specimens collected 
near Cedar Rapids, and am convinced that all are of the same species. 
In most of the specimens the outer mandibular cusps are larger than 
the four others. In other specimens the cusps are subequal. The 
usual number of cusps is six. Occasionally a specimen is found with 
seven cusps, and rarely one with five. 
There is no crest developed on the back of either sex during the 
breeding season, as is so characteristic of Petromyzon marinus. About 
one-fifth distance from the vent to the end of the tail a small fin-like 
crest is developed on the male. There is also a similar crest on 
the female, which is larger, less firm, and more fin-like. 
The dorsal fins on both males and females are situated on a small 
crest, which is more conspicuous on the males. 
The number of muscular impressions between the last gill opening 
and the vent vary from sixty-five to sixty-eight. 
A microscopical examination of the zoosperms shows those in both 
the specimens from Ithaca, N. V. , and Iowa, to be of apparently the 
same shape and size. The head is large and prismatic, with a long, 
slender tail, which usually has an enlargement near its posterior end. 
It is quite evident that this species is far more widely distributed in 
this country than was formerly supposed, and it will no doubt be found 
in all streams in the Mississippi Valley, at least north of the lower 
Ohio rivers. 
Early in the spring they leave the larger streams, and ascend the 
smaller streams to deposit their eggs, which occupies from one to two 
weeks. They make their nests in the bed of the stream by excavating 
