210 GEOL. AND NAT. HIST. SURVEY OF MINNESOTA. 
collector. This family undoubtedly is the link connecting the Daph- 
nide with the Lynceide, relationships to which are expressed by 
Macrothrix, on the one hand, and Lyncodaphaia on the other. 
The rank of this group as a family must be, of course, a matter 
largely of opinion. Sars was the first to adopt this view, sustained 
by certain curious transition forms leading toward Lynceidw. Later 
writers seem never to have found these genera and the group was 
again included with the Daphnide. The writer (82), npon the discov- 
ery of the Lyncodaphnia was forced to regard this group as of equiva- 
lent grade with the above mentioned families and again proposed the 
family name Lyncodaphnide. 
The genus Ilyocryptus is a little one side the normal course of the 
family and seems related to the lynceid genus Leydigia. 
The waters of the northern United States are very rich in members 
of this family. 
The aberrant family Bosminide finds its only connection with other 
Cladocera through this group by means of the remarkable Macro- 
thrix (2) pauper; and here it is only vaguely hinted at in the elongated 
antennules and angled lower margin of shell, as well as the presence of 
certain bodies near the base of the antennules. It has been affirmed 
that none of the Lyncodaphnide have an ephippium, i. e., the saddle- 
shaped thickening of the shell walls to include and protect the winter 
eggs; but I have discovered it in the case of Macrothrix tenuicornis 
Kurz and presume it may occur exceptionally in others. Kurz says 
that Ilyocryptus has no moult proper, but this probably refers only to 
the European J. sordidus. The American species differs from the 
generic description given by Kurz, and may be different in this 
respect also. 
In this family the regularity in the disposition of the sete on the 
antenne is broken and the fringing of these hairs serves the purpose 
of specific distinction. The antennules are always long and frequently 
differ considerably in the sexes. The pigment fleck is always present 
(Kurz is in error in denying its existence in Lathonura). In many 
forms there is no free posterior margin of the valves, while the lower 
is generally thickly beset with movable spines. The Lyncodaphnide 
will be distinguished from Ceriodaphnia, which they resemble, by their 
motion, which is a succession of quick bounds, while the broader 
Ceriodaphnie hobble along as though heavily weighted by the enor- 
mous mass of eggs with which they are generally laden. The abdomen 
is usually short and the anus is behind the terminal claws, but in Ily- 
ocryptus the claws are long and spined at the base. In the American 
I. spinifer the anal opening is elevated to a point nearly underneath 
the stylets, and there is a rudimentary anal czcum as in Lynceids. 
