224 THE AMERICAN NATURALIST. [VoL. XXXIV. 
2’. Abdomen not tuberculated. Inner branch of the uropoda reach- 
ing the extremity of the abdomen 
c. Ultimate segment of the abdenit ridged. Branches of 
uropoda of equallength. Sinus at extremity of abdomen 
funnel-shaped. 
Dynamene benedicti Richardson, D, surface 
c. Ultimate segment of abdomen smooth. Outer branch of 
uropoda but little more than half as long as inner branch. 
Sinus at extremity of abdomen small. 
Dynamene glabra Richardson, D, surface 
Genus Ciliczea Leach. 
a. Terminal segment with three sinuses, one above another in a longitu- 
dinal series, the two upper openings heart-shaped. Outer branch of 
the uropoda armed with four spines. 
Cilicea cordata Richardson, A, surface 
a’. Terminal segment with one sinus. Outer branch of the uropoda un- 
armed. 
b. Sinus without teeth. Cilicæa carinata Richardson, S, 440 fms. 
&. Sinus with teeth. 
c. Sinus with four teeth. Median tubercle at base of terminal 
segment single. . . Cilicea caudata (Say), M, surface 
c’. Sinus with six teeth. Median tubercle at base of termin 
segment double. 
Cilicea caudata gilliana Richardson, D 
"Genus Nesa Leach. . . . . . . JVesa (?) depressa Say, M, surface 
Nesa (?) ovalis Say, S, surface 
FAMILY XII. SEROLIDA. 
Genus Serolis Leach. 
Serolis carinata Lockington, D, 3 fms. (See Fig. 9, p. 225-) 
III. VALVIFERA. 
a. Body more or less broad, depressed. Legs usually nearly alike, but 
^ first three pairs sometimes with propodus dilated and dactylus reflexed. 
Family XIII. Idoteide 
a’. Body narrow, scarcely depressed. Four anterior pairs of legs unlike 
ree posterior pairs, and not ambulatory, nor strictly prehensile, 
directed forward, slender, ciliated, with terminal joint minute ; last 
three pairs stouter, ambulatory, with terminal joint bifid. 
Family XIV. Arcturide 
FAMILY XIII. IDOTEIDA. 
a. Sides of head emarginate or cleft and laterally produced beyond the 
eyes, which are situated upon its dorsal surface. Three anterior 
