24 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 24 



Streets, 1872, and several from the eastern Pacific, including P. crenu- 

 latus Lockington, P. ortmanni Nobili, P. lewisi (Glassell), P, hians 

 Nobili, and two species described herein. 



Several species not treated in this report, including Petrolisthes 

 novaezelandiae Filhol, 1885, P. penicillatus (Heller), 1862, and P. 

 tomentosus (Dana), 1852, do not fit into any of the categories outlined 

 above. 



Key to the Eastern Pacific Species 



la. Epibranchial spine present (rarely obsolescent, its position 

 distinctly marked at epibranchial angle) ; anterior margin of 

 merus of walking legs spined 2 



lb. No epibranchial spine; anterior margin of merus of w^alking 

 legs without spines (in P. hirtipes, 1 or 2 minute spinules oc- 

 casionally present on dorsal surface near epibranchial angle; 

 anterodistal angle of merus of walking legs sometimes spine- 

 tipped) 13 



2a. Carapace with distinct, transverse, piliferous striations, inter- 

 rupted only at grooves defining the various regions. . . 3 



2b. Carapace smooth to rough, but never with transverse stria- 

 tions as in 2a 8 



3a. Carapace with groups of spines on hepatic, protogastric, and 

 epibranchial regions, and a row of marginal mesobranchial 

 spines, in addition to the usual epibranchial spine. 



sanfelipensis 



3b. No spines on dorsal surface of carapace; no marginal meso- 

 branchial spines 4 



4a. A single epibranchial spine 5 



4b. Two epibranchial spines glasselli 



5a. Carpus with 3 low, wide-set teeth on anterior margin. . . 6 



5b. Carpus with 4 or 5 broad, close-set teeth on anterior margin. 7 



6a. Carpus about twice as long as wide, covered with large flat- 

 tened tubercles; striations of carapace interrupted at meta- 

 branchial regions edwardsii 



6b. Carpus about 3 times as long as wide, with 3 longitudinal rows 

 of rugae; striations of carapace continuing across metabran- 

 chial regions agassizii 



