ENTOCYTHERE CAMBARIA {nov. gen. et nov. spec.), 
A PARASITIC OSTRACOD. 
BY WM. S. MAESHALL, 
Assistant Professor of Zoology, University of Wisconsin. 
While examining a number of branchiae taken from recently 
killed crayfish, I noticed on one of themi a small crustacean, 
which upon examination with a microscope, proved to he an 
Ostracod. The peculiarity of its habitat at once struck me as 
anomalous, and desiring to procure more specimens, I adopted 
the following method which I found very satisfactory. When 
any specimens of the Ostracod were wanted a, crayfish was 
killed, the branchiae removed and placed in a large watch-glass 
partially filled with water. The contents of this glass being 
examined a few minutes later, the Ostracods, if present, were 
found near the edge of the water at the side farthest from the 
light, to which they appear very sensitive. As soon, as the 
branchiae were placed in the water the parasites would leave 
them] and reaching the glass would crawl along it until they 
came to the edge of the water, where they would remain as far 
from the source of light as possible. 
The first crayfish (different species of Cambarus ) examined 
were from the vicinity of Madison; of these, nearly half were 
infected. Other crayfish were obtained through a dealer and 
varied considerably in their infection; some localities yielding 
nearly as high a percentage as those near Madison, while cray¬ 
fish from other localities appeared to be entirely free. The 
dealer obtained this material from different parts of Wiscon¬ 
sin, but I could get no definite locality other than Madison. At 
no season of the year were the p fftes entirely absent although 
