No. 399.] WORTH-AMERICAN INVERTEBRATES. 223 
V. Extremity of terminal abdominal segment not produced. 
c. Surface of abdomen tubercular. 
d. Uropoda not reaching apex of terminal segment ; outer 
branch the shorter and not denticulate. Terminal 
segment with eight tubercles. 
Spheroma octoncum Richardson, D 
d'. Uropoda surpassing the apex of the terminal segment ; 
outer branch the longer and provided with four teeth 
on external margin. Terminal segment with four 
tubercles. 
Spheroma destructor Richardson, Florida fresh-water 
c. Surface of abdomen smooth. ; 
d. Outer branch of the uropoda denticulate on its external 
margin. 
Spheroma quadridentatum Say, MS, surface to % fm. 
4. Outer branch of the uropoda not denticulate. 
e. Outer branch of the uropoda half as long as the 
inner branch, and half as wide. 
Spheroma thermophilum Richardson, New Mexico, fresh-water 
c. Outer branch of the uropoda not much shorter than 
inner branch, and of equal width. 
Spheroma oregonensis Dana, APD, surface to 12 fms. 
Genus Tecticeps Richardson. 
a. Terminal segment of abdomen pointed. Outer branch of uropoda 
much longer than inner branch. First pair of antenna reach the 
posterior angle of the first thoracic segment. Second pair reach the 
middle of the second thoracic segment. Sixth and seventh pair of 
legs show a marked disproportion in the length of the propodus. 
Tecticeps alascensis Richardson, A, 9-106 fms. (See Fig. 8, p. 221.) 
a’. Terminal segment of abdomen widely rounded. Outer branch of uro- 
poda not longer than inner branch. First pair of antenne reach the 
posterior angle of the third thoracic segment. Second pair of antenne 
reach the middle of the fourth thoracic segment. Sixth and seventh 
pairs of legs show only a gradual increase in length. 
Tecticeps convexus Richardson, D, 5 fms. 
Genus Dynamene Leach. 
a. Frontal margin of head produced in a quadrangular process ; first two 
joints of the first pair of antennz dilated. 
Dynamene dilalata Richardson, D, surface 
a’. Frontal margin of head not produced ; joints of first pair of antenna 
not dilated. 
b. Abdomen tuberculated. Neither branch of the uropoda reaching 
the extremity of the abdomen. 
Dynamene tuberculosa Richardson, A D, surface 
