ENTOMOSTEACA OF MINNESOTA. 223 



The above is extracted verbatim from the Alabama Crustacea, which 

 Professor Birge should have consulted before saying "none of the 

 specific characters are mentioned or figured" (Birge '91). 



Professor Birge is inclined to identify our species with I. longiremis 

 Sars, from Australia. But if the Madison specimens have antennary 

 setie nearly equaling the total length of the animal, they differ from 

 all individuals of I. spinifer yet seen. The armature of the post-ab- 

 domen is also different, for there are but four elongated claws at the 

 inferior angle and a series of about 14 anal sj)ines and six longer supra- 

 anal teeth. We infer from Birge's figure that the antennae are dif- 

 ferent. It would be well that the Madison form should be more care- 

 fully described and figured and compared with other American species. 

 Length 0.60 mm., height 0.46 mm., base of antenna 0.19 mm., four- 

 jointed ramus 0.13 mm., post-abdomen 0.19 mm., claw 0.125 mm., long 

 post anal spines 0.06 mm., antennule 0.10 mm. 



Ilyocryptiis aciitifrons Sars. 

 Plate LV, Fig. 7. 



This species is only mentioned in the appendix to the paper of Sars 

 on the Cladocera from the vicinity of Christiauia. The following is a 

 condensation of the description. 



Head large, acute in front. Shell truncate behind, with shorter 

 sette behind than below. Autennules shorter and thicker than in 

 I. sordidus. Antennse long and robust. Abdomen with a short, obtuse 

 process. Post-abdomen shorter than in I. sordidus, posterior margin 

 continuous, anus terminal; caudal claws straight, very long, with two 

 minute basal spines and a cluster of teeth in front. Pigment fleck 

 almost touching the eye. Length less than in J. sordidus, 0.6 mm. 



In this species the moult is perfect. (See table above.) 



* Ilyocryptiis longiremis Sars. 

 Plate LV, Fig. 5. 

 Sars '88; Birge '91. 

 Professor Birge finds this species abundant near Madison. The 

 original description is not now accessible. It appears, however, that 

 the form of the post-abdomen is very similar to I. spinifer, while its 

 armature is quite different. The setse of the antennae are very long, 

 nearly equaling the length of the body. There are five to seven 

 super- anal teeth, largest in the middle, an outer row of about eight 

 long post anal spines and an inner row of 11 to 12 post-anal denticles, 

 besides several very small teeth near the terminal claw. There are 

 three or four denticles on each side of the anus. The moult is incom- 

 plete as in I. spinifer. 



