33 



GENUS 7. 

 Acroperus. Baird, 1850. 



Acroperus, e. p. Schodler. 



Acroperus. Miiller, Sars, Kurz. 



■ 



SPECIES 1. 



Acroperus Leujocephalus. Koch. 



Lynceus leucocephalus, Koch. 1. c, H. 36, PI. X. 



? A. harp^e. Baird, 1. c, p. 129, PL XVI, fig. 5. 



L. leucocephalus. Fischer, Ergaazung, u. s. w., 1854, p. 11, PI. Ill, 



fig. 6-9. 

 A. leucocephalus. Schodler, Miiller, Kurz. 



Cambridge, Mass., Madison, Wis. Common. 



Kurz says: " Die Acroperusarten sind die besten Schwimmer 

 unter den Lynceiden.'' This is not true of our species, which is 

 far inferior in strength and rapidity of motion to both Crepido- 

 cercus and Pleuroxus. The same is true of Alonopsis and Alona. 



The last genus, indeed, is given to haunting the bottom of the 

 water, and often is found resting among the debris at the bottom 

 of the jar in which it is kept. 



GENUS 9. 



Camptocercus. Baird, 1851. 

 Camptocercus. Baird, Sars, Schodler, P. E. Miiller, Kurz. 



SPECIES 1. 



Camptocercus Macrurus. 0. F. Miiller. 



Length, about 1 mm. 



Lynceus macrurus. O. F. Miiller, Prod. No. 2397. 



Liljeborg, 1. c, p. 89, PI. VII, figs. 2, 3. 

 Camptocercus " Schodler, Neue Beitr., p. 35, PI. II, figs. 39-41. 



P. E. Miiller, 1. c, p. 164, PI. Ill, fig. 12. 



Cambridge, Mass., Madison, Wis. ISTot common. 



SECTION II. GYMNOMERA. Sars. 



Polyphemus Pediculus. De Geer. 

 One specimen only. Cambridge, Mass., Oct., 1876. 



