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 (AMMOTHEID^E\ 



B. Body rather elongate, distinctly segmented ; lateral processes well 

 separated; chelifori i -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 pair of legs .... Ammothea latifrons, 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 g-jointed (Ammothella}. 



E. Eye tubercle low, rounded ; first 2 or 3 trunk segments 

 with a conical tubercle dorsally near the posterior border. 



Ammothella tnbcrculata, 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 i-, sometimes 2-jointed; palpi 6- or 7-jointed. 

 (Tanystylum). 



