STATE GEOLOGIST. 175 



jointed; the outer ramus of the fourth foot is two-jointed; the fifth 

 pair is absent or rudimentary. Tlie abdomen is four or five-jointed, 

 and the stylets are rather short. Ova-sacs two, large. 



Ergasilus depressus, Sars. 



(See Forhandlinger i Videnskabs-Selskabet, 1862.) 



The form figured in plate S., fig. 1, is known from a gathering 

 taken under the same circumstances as Sars' specimens, and con- 

 sisted only of males. The animal is very transparent with deep 

 blue markings below, especially between the bases of the feet. 

 Sars thinks the males are always free, while the females early re- 

 tire to the gill-cavities of fishes. This species may be distinct from 

 the Norwegian form, but there is no reason for declaring that it is 

 so. 



E. depressus is probably the young of the widely distributed E. 

 sieboldii. 



Note. — As the systematic part of this work draws to a close, a 

 note is received from Prof. Birge, who was so kind as to glance 

 through advance sheets of the portion upon Cladocera. Prof. Birge 

 informs me that his Scapholeberis nasuta is the same as S. (Daph- 

 nia) aurita, Fischer, as published in 1849 in the Bull. Natur- 

 forsch. Gesellsch. in Moscaii, Bd. 22. This paper I have not seen. 

 At Prof. Birge's suggestion, then, read on page 43. 



Sp 4, Scapholeberis aurita, Fischer. 



Daphnia aurita, fischer. 

 Scapholeberis nasuta, birge. 



