STATE GEOLOGIST. 55 



D. pellucida, P. E. Mueller. 

 D, galeatE; Sars, 

 12. ( ?) D. laevis, Blrge. 



Section ir. Pigment fleck absent. 



A. Head but slightly crested. 



1. D. longiremis, Sars. 



B. Head strongly crested. 



2. D, cristata, Sars." 



3. D. cucuUata, Sars. 



D. apicata, Kurz . • 



4. D. kcdbergensis, Schoedler. 

 D. cederstromii, Schoedler. 

 D. retrocurva, Forbes, 



D. vitrea, Kurz. 



5. D. magnicepSySp. n. 



SECTIOiq" I. 



A. Head shorty evenly curved. 



Sp. 1. Daphnia psittacea, Baird. 



Mentioned by Schoedler, Frig and Kukz. 



This species is at once recognized by the head, which is very 

 short and evenly curved, or nearly so, from the heart to the beak. 

 The shell is high, oval, with a rather short spine. The fornices 

 are wide and angled behind: the antennules are longer than in 

 most species; the post-abdomen is very large, but narrows toward 

 the end and has comparatively few anal teeth, which are of une- 

 qual bize. This is one of the largest of the genus. Not yet 

 found in America. 



B. Head more or less concave below, at least not evenly arched. 



Sp. 2. Daphnia schseflPeri, Baird. 

 (Plate M. Fi^s. 1—4.) 



Daphnia pennata, MuELLiER. 



Daphnia pulex, STRAUS, KOCH, (fide P. E. MUELLER.) 

 Daphnia magna, LiLLJEBORG, LErDIG, etc. 

 Daphnia schsefferi, SCHOEDLER, KuRZ. 



The largest species of the genus, is of an elongated oval and 

 ventricose form. The spine is entirely absent in old females and of 

 only moderate length in the young. The antennules of the male 

 are long and have a very long flagellum. The post-abdomen is 

 narrowed suddenly below the anus so that the spines consist of 

 two sets; the terminal claws are spiny at the base. Although 



