24:6 TENTH ANNUAL REPORT 



bordering the egg-cavity and a little beyond, is composed of large and 

 very deep cells ; the space between the outer and inner layers is much 

 greater than in Daphnia. 



Genus lathonura. 



Although no species of this genus has been found in Minnesota, it 

 is to be expected that it will eventually be discovered that the 

 cosmopolite L. rectirostris, Miill. occurs in our limits. It occurs in 

 Mass, according to Birge. The figures (Plate VIII, figs. 11-12) 

 were drawn from specimens found in Leipzig, Saxony, illustrating a 

 tendency, especially common in the Lyncodaphindce, to abnormal 

 growth of the spinous appendages — in this case the anal setae. 



Genus iliocryptus. 



A genus represented by a single European species. Our form may 

 differ somewhat in some respects from the generic diagnosis, but 

 certainly belongs here. There are no anterior cceca (as indeed there 

 are probabl}^ not in the European /. sordidus though so stated by 

 Miiller,) and no permanent coecum or dilation of the intestine before 

 the rectum. The marginal spines are straight, long and movable with- 

 out branches. 



ILIOCRYPTUS SPINIFER Sp. nOV. 



(Plate YIIT, figs. 2-6.) 



Short; depth nearly equaling length of body excluding head; rounded 

 behind; free edges of valves beset with slender ciliate spines which are 

 not branched; antennae exactly as those of /. sordidus, as is the post- 

 abdomen, save that the anus seems to be situated higher; ova three or 

 more. 



This species occurs in Silver lake, east of Minneapolis. It swims 

 quite well, while of the European species it is said this is not the case. 

 It does, however, frequently load itself with filth so as to be too heavy 

 to swim freely. 



