ENTOMOSTRACA OF MINNESOTA. i 
A large robust species (2.5 to 3.0 mm. long), with the last abdomi- 
nal segment produced into two long acuminate and mucronate lobes. 
The first abdominal segment is also produced and spined. The an- 
tenne are short, barely reaching the second abdominal segment. The 
third joint of the outer ramus of the fifth foot is large and furnished 
with two unequal spines, one being very long. The claw is short and 
serrate. The inner ramus is two-jointed and armed with one very 
long and one short spine. The inner ramus of the right foot is two- 
jointed, and of the left, one-jointed in the male. 
Two varieties or subspecies are recognized as separate species, but 
Seem to be due to difference of station simply. 
Diaptomus glacialis Lilljeborg. 
PLATE IX, Fie. 8. 
De Guerne and Richard ’89. 
The last two thoracic lobes are confluent dorsally and are produced 
into even longer lateral processes than D. castor. Processes of the 
rostrum differ from those of D. castor in being elongate, sinuate, and 
obtuse. The fifth feet of the male differ chiefly in that the inner ra- 
mus of the right leg is very indistinctly two-jointed. There is oc- 
casionally a rudimentary appendage upon the antepenult segment of 
the male antenna. 3.0 mm. long. Glacial waters of Nova Zembla, etc. 
Diaptomus mirus Lilljeborg. 
PLATE VIII, Fia. 8. 
De Guerne and Richard ’89., 
A species or variety even larger than D. castor (3.6 mm. long) and 
differing very little from D. glacialis. The lateral projections from 
the last thoracic segment (which is distinct) are smaller, and the first 
abdominal segment is not produced into great lateral processes. The 
fifth feet are almost identical in the two species. The fifth feet of 
the males differ only in the proportional development of the parts. 
The form was found in Siberia by the Nordenskidld expedition. 
Diaptomus sancti-patricii Brady. 
PLATE XXXIII, Frias. 9-11. 
Brady 791. 
Posterior angles of the last thoracic segment very much produced 
so as to form attenuated spines. Anterior antenne reaching about as 
far as apex of furca; penultimate joint of the anterior antenna of the 
male entirely destitute of marginal process. Inner branch of the fifth 
pair of feet in the female indistinctly biarticulate, nearly as long as 
