174 Miss H. Richardson on the Isopods of the 



tlie posterior margin of the corresponding segments, while 

 with A. Icevis they are all very small and somewhat spini- 

 form in the fiftii to the seventh segments ; in the greater 

 breadth posteriorly of the terminal segment of the body in 

 A. Icevis^ and in the shape and length of the uropoda in the 

 two species, the two branches being of unequal length, 

 lamellate in shape (the inner one the longer), and both shorter 

 than the last segment of the body in A. Icevis, while in 

 A. californica they are equal in length, similar in shape, 

 oar-like, and longer than the terminal segment. 



Family VIT. Sphaeromid*. 

 Analytical Key to the Genera of Spha^romida^. 



a. Both exterior and interior branches of uropoda pro- 

 jecting. 

 b. Terminal segment of the abdomen excavated at its 



extremity 12. Dynamene. 



b' . Terminal segment of abdomen entire. 



c. Margins of head not produced; antennae con- 

 spicuous ; legs normal ; mandibles with five- 

 jointed palp 13. Spharoma. 



c'. Anterior and lateral margins of head produced, 

 concealing antennpe; propodus of first and 

 second pairs of legs dilated, with retlexed 

 dactylus ; mandibles with three-jointed palp. . 14. Tecticeps. 

 a'. Only exterior branch of uropoda projecting ; penul- 

 timate abdominal segment in male generally pro- 

 duced in spine ; terminal segment excavated with 

 median tooth 15. Ciltctpa. 



12. Dynamene, Leach. 



Analytical Key to the Species of Dynamene. 



a. Frontal margin of head produced in a 

 quadrangular process ; first two joints 



of fir,«.t pair of antennae dilated 21. Z). dilatata, sp. n. 



a . Frontal margin of head not produced ; 

 joints of first pair of antennae not 

 dilated. 

 b. Abdomen tuberculated. Neither branch 

 of uropoda reaching extremity of ab- 

 domen 22. D. tuberculosa, sp. n. 



b' . Abdomen not tuberculated. Inner 



branch of uropoda reaching extremity 



of abdomen. 



c. Ultimate segment of abdomen ridged. 



Branches of uropoda of equal length. 



Sinus at extremity of abdomen 



funnel-ehaped 23. D. benedicti, sp. n. 



