258 COLE 
KEY TO THE SPECIES 
The following key is adapted only to the species of Pycno- 
gonida described in this paper, and is applicable only to adult 
forms. If a chelate specimen not positively known to be adult 
cannot be identified by it, the specimen may be an immature in- 
dividual and can perhaps be traced by considering it under A, 
forms with “ Chelifori present, not chelate in adult.” 
A. Chelifori present, not chelate in adult; palpi present; ovigera 10- 
jointed, present in both sexes (AMMOTHEID2Z). 
B. Body rather elongate, distinctly segmented ; lateral processes well 
separated; chelifori 1-jointed; palpi g-jointed (Lecythorhyn- 
chus). 
C. Proboscis subcylindrical or elliptical, constricted in its middle 
third ... . . . Lecythorhynchus marginatus, p. 260 
B’. Body more or less disciform ; segmentation often indistinct ; lateral 
processes approximated. 
C. Chelifori 2- or 3-jointed; palpi 8- or g-jointed. 
D. Chelifori 2-jointed; palpi 8-jointed (Ammothea). 
E. Chelifori more than half as long as proboscis; caudal seg- 
ment reaching at least to middle of second coxal joint of 
fourth pairoflegs . . . . Ammothea laiifrons, p. 263 
E’. Chelifori less than half as long as proboscis. 
F. Proboscis narrow, fusiform; forms less than 4 mm. in 
length and 20 mm. in extent. 
G. Protuberance on dorsal side of first coxal joint about 
half as long as the joint; genital protuberance in 
male of about the same length. 
Ammothea alaskensis, p. 266 
G’. Protuberance on dorsal side of first coxal joint fully 
three fourths as long as the joint; genital protu- 
berance in ¢ only about half as long as protuberance 
on first coxal joint . . Ammothea gracilipes, p. 269 
F’. Proboscis broadly clavate, truncate at the apex; forms 
over 4 mm. in length and 20 mm. in extent. 
Ammothea pribilofensis, p. 270 
D’. Chelifori 3-jointed; palpi 9-jointed (Ammothella). 
E. Eye tubercle low, rounded; first 2 or 3 trunk segments 
with a conical tubercle dorsally near the posterior border. 
Ammothella tuberculata, p. 273 
E’. Eye tubercle tall, slender; caudal segment slender, curved, 
elevated, spinose; first and second trunk segments with 
a pair of spines dorsally near the posterior border. 
Ammothella spinifera, p. 275 
C’. Chelifori usually 1-, sometimes 2-jointed; palpi 6- or 7-jointed. 
( Zanystylum). 
