OF DENISON UNIVERSITY. 
39 
the family and has been seen but few times. First described and 
figured by Fischer, from Russia, it next turns up in Scandinavia, where 
Sars gives a full Latin description. Norman and Brady find it in 
England, and Mueller in Denmark, and, finally, Hellich records it in 
Bohemia. It was also reported from Minnesota, by the writer, 
in 1884. 
Unlike most other limicole cladocera, the body is narrow and high, 
rather than globose, the head is much depressed and terminates in a 
slender rounded beak, like the bill of a duck. The fornices or free 
margins of the head-shield are narrow and flaring. The shell of an 
old individual is a curious pile of overlapping valves, and is ornament- 
ed with concentric series of depressions. The lower margin is nearly 
straight and bears a row of long curved teeth (not free spines), back 
of which are two small teeth. The antennae are short and the an- 
tennules rather slender. In this respect our specimen seemed to dis- 
agree with the figure given by Hellich. The labrum is of large size 
and is produced into an acute appendage below, as in most Lynceids. 
The compound eye is quite absent, but its function is subserved by the 
larval organ, a quadrate and rather large fleck at the base of the an- 
tennules. The intestine is coiled once and one-half times and opens 
in about the middle of the flat, pentagonal post-abdomen. The latter 
bears straight terminal claws, each with a single basal spine, a series of 
rather small triangular teeth, posteriorly, and irregular areas of fine 
spines upon the sides. The male is not known and many points of 
interest remain to be made out. 
The two species of Leydigia^ both of which occur in America, are 
familiar enough and are sufficiently well described to render a repeti- 
tion of the description needless. It is otherwise with the only species 
of llyocriptus yet found in America. 
Ilyocryptus setifer, Herrick. — The description given in my 
“Final Report, etc.,” is very brief and no comparisons were there 
instituted with the I. agilis of Kurz which is its nearest ally in 
Europe. The paper by Kurz referred to gives detailed descriptions of 
the three European species accompanied by elegant plates. We are 
able, therefore, to draw up the following distinctive diagnosis of the 
species, hoping thereby and by means of the figures to show the rela- 
tions of the four species at present known. It is almost certain that 
we have more than one species in America and the careful description 
of the known form may make the detection of others easier. 
