IV. 
MUD-INHABITING CRUSTACEA. 
Plate IX. 
Among the curiosities of pond life are certain minute crustaceans 
which spend their entire life in the soft debris and mud forming the 
superficial deposit at the bottom. The Canthocarnptus among cope- 
pods is commonly found in such situations, but this is less surprising 
than that members of the cladocera, or shelled entomostraca, with their 
delicate organization and frail structure should have become adapted 
to such a life. In many marine crustaceans (copepoda) the accomo- 
dation to such a reclusive life is manifested in the retrograde devel- 
opment of many of the organs — eyes, even, being absent in several 
cases. The present paper is concerned only with a few cladocera, 
which are peculiar to America or rare both here and elsewhere, and 
which exhibit curious and instructive modifications as a result of such 
a habitat. The reader who wishes to familiarize himself with the sys- 
tematic classification of the group would do well to consult Die Clado- 
ceren Boehmens^ by Hellich, Birge’s Notes on Cladocera, and the 
writer’s Final Report 07 t Crustacea of Minnesota, while, for a thor- 
ough study of the physiology, Weisman’s Beitraege zur Naturgeschiclite 
der Daphnoideii, is necessary. A special paper on the limicole or 
mud-loving cladocera was published in the Zeitschrift fuer Wissenchaft- 
liche Zoologie, in 1878, by Dr. Win. Kurz, and entitled Ueher limi- 
cole cladoceven. Reference will be frequently made to this paper and 
this must be understood in all cases of reference to Kurz, unless other- 
wise specified. These mud-dwellers are happily called schniutz-pe- 
terchen^^ cladocera, i. e. ‘‘Smut-Johnny,” or chimney-sweep water 
fleas. In America the following species are pre-eminently worthy of 
the name : Mofiospilus tenuirostris, Leydigia quadrangidaris, Alona 
sanguinea, Alona quadra 7 igula, Pleuroxus procm'vus, and several other 
members of the genera Alona and Pleuroxus. The typical cladocera 
