ENTOMOSTRACA OF MINNESOTA. 75 



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- 

 tennae 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. 



Diaptoiniis glacialis Lilljeborg. 



Plate IX, Fig. 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 inirus Lilljeborg. 

 Plate VIII, Fig. 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 N^ordenskiold expedition. 



Diaptoniiis sancti-patricii Brady. 



Plate XXXIII, Figs. 9-11. 



Brady '91. 



Posterior angles of the last thoracic segment very much produced 



so as to form attenuated spines. Anterior antennae reaching about as 



far as apex of furca; penultimate joint of the anterior antenua 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 



