ENTOMOSTRACA OF MINNESOTA. 221 



* Ilyocryptus spinifer Herrick. 



Plates LV, Figs. 1-4; LVI, Figs. 18-19, 21. 



Herrick '82, '84, and '87; Tamer '93. 



The description given in my Final Eepoit, etc., is very brief, and no 

 comparisons were there instituted with the I. agilis of Kurz, which is 

 its nearest ally in Europe. The paper by Kurz referred to gives de- 

 tailed descriptions of the three European species, accompanied by ele- 

 gant plates. We are able, therefore, to draw up the following dis- 

 tinctive diagnosis of the species, hoping thereby and by means of the 

 figures to show the relations of the four species at present known. It 

 is almost certain that we have more than one species in America, and 

 the careful description of the known form may make the detection of 

 others easier. 



The size varies greatly; a full grown female with eggs in the brood 

 cavity is nearly 0.90 mm. long and 0.70 high, while a smaller female 

 measures 0.65 mm. long by 0.44 high. The form of the shell is nearest 

 like that of J. acutifrons, the height being less than in I. sordidus, and 

 the angle between the ventral and posterior margins less than in 1. 

 agilis. The entire length of the post-abdomen in the large female is 

 0.56 mm. measured to the base of the candal stylets, of which length 

 0.168 mm. pertains to the claws. The width of the post abdomen is 

 but 0.14 mm. Thus it is evident that the proportions of the post- 

 abdomen differ greatly from any of the other species, it being very 

 long and narrow. The terminal claws are exactly as in I. agilis, hav- 

 ing two small basal spines and a few sharp serrations near the apex, 

 anteriorly. Near the base of the claw is a cluster of small spines of 

 two sizes, then begins a series of about 16 lateral teeth averaging 

 0.02 mm. in length and extending to the sides of the anus. Above 

 this point the contour of the margin is convex and is ornamented with 

 nine spines twice as long as the preceding. Then follow the promi- 

 nences which bear the long and simple caudal setse. Besides the 

 above mentioned spines there are four spines on either side upon the 

 lower posterior angle of the post-abdomen which are four times as 

 long as those of the previously mentioned continuous series (i. e., 0.08 

 mm.). Above, the abdomen is hirsute or thorny as in 1. agilis, and 

 the process for closing the brood sac is similar. It will be seen that 

 the post-abdomen differs in armature as much as in form from other 

 species. From I. sordidus it differs in the following points: The 

 claws are not pectinate behind but are serrate in front, the anal open- 

 ing is higher and the details of the spines vary; from J. acutifrons it 

 differs in that the claws are not pectinate, neither is there a spine in 

 front of the claws, and the anus is not terminal; from J. agilis it differs 

 in that the shape is dififerebt, there are fewer enlarged spines, and the 



