STATE GEOLOGIST. 



77 



Sp. 2. Ilyocryptus spinifer, Herrick. 

 (Plate C. Figs. 18—19.) 



Usually longer than high; head rounded, almost exactly like T. 

 sordidus, but the form of the post-abdomen differs a little in the 

 higher situation of the anus and the great elongation of four or 

 five of the lower spines of the posterior margins; the margins of 

 the shell are beset with pectinate setse which do not branch. The 

 nearest approach to branching setae yet seen are figured on plate C, 

 fig. 18 a; this consists in the outgrowth of a spine from near the 

 base, and such setse are found only on part of the posterior margin. 



It seems that our form is rather close to I. sordidus though 

 clearly distinct. 



This species occurs in many of our lakes, and is found most fre- 

 quent in late summer. 



Sp. 3. Ilyocryptus acutifrons, Sars. 



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

 Sars on the Cladocera from the vicinity of Christiania. The follow- 

 ing is a condensation of the description. 



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

 setae behind than below. Antennules shorter and thicker than in 

 I. sordidus. Antennae 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. Pigment fleck almost touching the 

 eye. Length less than in I. sordidus. 



This species seems in some respects more like a true lyncodaph- 

 nid than either of the other species. It is doubtful if it belongs 

 here. 



FAMILY LYNCEIDiE. 



1. Eurycercus 



2. Acroperus 



3. (Jamptocercus . 



4. Alonopsis 



5. Leydigia 



6. Graptoleberis.. 



7. Crepidocercus . 



8. Alona 



9. Alonella 



10. Pleuroxus 



11. Harporhynchus 

 2. Cliydorus 



13. Anehistropus... 



14. Monospilus 



Totals 



Number 



of 

 known 

 species. 



1 



2 



6 



3 



2 



2 



1 

 21 



5 

 14 



8(?) 



1 



1 



68 



Europ- 

 ean. 



14 



5 

 8 



6(?) 



1 



1 



50 



Also in 

 America 



20 



In 



America 

 only. 



Total 

 Amer- 

 ican. 



3 



1(?) 

 1 



