134 THE AMERICAN NATURALIST. (VoL. XXXIV. 
D’. Carpus of chelipeds with one spine at inner angle. 
E. Antero-lateral teeth with dentate or spinulous margins. 
F. Crests on hand feeble, granulate 
C. anthony? Rathbun D 
F'. Crests on hand strong, the upper ones spinulous 
C. borealis Stimpson NM 
E'. Antero-lateral teeth with margins simply granulate 
C. irroratus Say NMS 
C'. Color on the fingers extending from the tip more than half the 
length of the fingers. 
D. Fronto-orbital width one-third the width of the carapace 
. antennarius Stimpson APD 
D’. Fromto-orbital width nearly one-half the width of the 
carapace. Carapace strongly areolated. 
E -G 
Fie. 2. — Tel het 
5 
E. Front truncate. Movable finger almost entirely 
k-colored . . C. oregonensis (Miers) APD 
E'. Front not truncate. Movable finger not more than 
two-thirds dark-colored . C. amphietus Rathbun D 
Genus Telmessus White - + + « « WZ, chetragonus (Tilesius) AP 
Genus Erimacrus Benedict’ o + + « « + + HE. tsenbeckit (Brandt) A 
KEY TO THE GENERA OF THE FAMILY PILUMNID.;E. 
A. The ridges that define the efferent branchial channels, if present, are 
low, and are confined to the posterior part of the endostome, never 
reaching to the anterior boundary of the buccal cavern. 
B. Fronto-orbital border less than half the greatest width of the 
carapace. 
