No. 26.] ARTHROSTRACA OF CONNECTICUT. 47 



The species is abundant and widely distributed. It has been 

 reported from the Arctic Ocean, Norway, Great Britain, France, 

 Greenland, Nova Scotia, Grand Manan ; Eastport, Maine ; Salem, 

 Woods Hole, Massachusetts ; off Fishers Island, New Haven, 

 Noank, Connecticut. 



It is found commonly in the jelly fish, Aurelia. Sars states 

 that several individuals, males, females, and young, may occur 

 in each medusa. 



Miss Rathbun in her List of the Cnistacea of New England 

 notes that Hyperia medusarum has been found off New Haven 

 and at Noank. In the material at my disposal I was unable to 

 identify H. medusarum, and am inclined to believe that H. galba 

 is the only Hyperid occurring in the waters of the State. 



GAMMARIDEA. 



Head not fused with first segment of thorax, and not tumid ; 

 maxillipeds with palp of 2 to 4 joints ; coxal plates always well 

 developed ; eyes simple or compound, of various sizes, but never 

 covering whole side of head ; gills present on 5 or 6 segments ; 

 first uropod always biramus. Hepato-pancreatic tubes generally 

 4, occasionally 2; rectal glands 2 or i, sometimes rudimentary; 

 heart with 3 pairs of ostia, rarely one pair. 



Typical Amphipoda. 



Key to the Genera of Gammaridea. 

 A. Mandible not denticulated, palp 3-jointed; antenna I with stout 

 peduncle and accessory flagellum well developed; coxal 

 plates deep; gnathopod 2 elongated and slender, ischium 

 elongated, propodus small and densely setose, dactyl rudi- 

 mentary (Lysianassidae). 



B. Telson entire Lysianopsis p. 51 



BB. Telson cleft. 



C. Postero-lateral angle of third abdominal segment not 

 greatly produced. 

 D. Mandibular palp inserted directly above molar tubercle 



Tmetonyx p. 54 



DD. Mandibular palp inserted behind molar tubercle 



CC. Postero-lateral angle of third abdominal segment 



Orchomenella p. 58 

 produced, with a deep sinus above. 

 D. Peduncular joints of antenna l produced distally 



Hippomedon. 



