392 Wisconsin Academy of Sciences, Arts and Letters. 



Species 29. Ophryoxus gracilis, Sars. Plate XIII. Figs. 10-12. 

 1862. Ophryoxus gracilis Sars, G. O. Oversigt af de i Omegnen af 

 Christiania jagttagne Crustacea cladocera, p. 158. Descrip- 

 tion of male and female. 

 (?) 1875. Ophryoxus paradoxurus, Hudendorff, A. Beitrag zur Kennt- 

 niss der Susswasser-Cladoceren Russlands, p. 43. Descrip- 

 tion of female. Tab. II., fig. 1, a. b. This species, founded 

 on a single specimen, very possibly belongs here. 

 1882. Lyncodaphnia macrothroides, Herrick, C. L. American Natural- 

 ist, Vol. XVI, p. 1006. Description of female. Plate XVI. 

 figs. 1, female, 2, antennae, 3, post-abdomen, 4, antennule. 

 1884. Lyncodaphnia macrothroides, Herrick, C. L. Geol. and Nat. 

 Hist. Survey of Minnesota, 12th Annual Report, 1884, p. 74. 

 Description of female. PI. B, fig. 12, yg.; 13, labrum; 14, anten- 

 nule; 15, last foot. PI. B, 1, figs. 1, female; 2, post-abdomen; 

 3, antennule. 



Ophryoxus is quite abundant in Lake Wingra, occurring through the 

 the entire summer in openings in the marsh. It i£ nowhere rare, and 

 never very plentiful. It seems to have the habit of a Daphnia, 

 swimming feebly about in the open waters, rather than clinging to 

 weeds. I give figures of the head, first leg, and the post-abdomen of the 

 male, which have never been illustrated. 



The statement that the young have a long spine, (Sars), or that the 

 young differ in form from the adult (Herrick), need qualification. The 

 form never differs greatly from that of the adult, and there is never any 

 difficulty in recognizing it as the young of Ophryoxus. Indeed, the pres- 

 ence of the spine is the only important difference between the young and 

 old. This spine is not long according to the standard of the genus 

 Daphnia as it rarely measures more than % °f the length of the animal . 

 It is possessed by the male as well as by the young female. In the adult 

 female it is reduced to a sharp prominence, like that seen in many 

 species of Ceriodaphnia. 



Species 31. Ilyocryptus longiremis, Sars. Plate XIII, fig. 18. 

 1888. I. longiremis, Sars. Additional notes on Australian Cladocera, 

 Christ. Vid.-Selskabs Forhand. 1888, No. 7, p. a3-41. De- 

 scription of male and female. PI. iv. figs. 1, female; 2, female 

 from below; 3, spines from edge of shell; 4, female post- 

 abdomen; 5, male. 

 I am unable to distinguish our specimens from those raised by Sars 

 out of mud from Australia. The antennary setae, from whose length the 

 name is derived, are even longer in our species than in Sars' figures, 

 nearly equalling the total length of the animal. There are 5-7 super- 

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

 anal spines and an inner row of 11-12 post-anal denticles besides several 



