FISHERY BULLETIN: VOL. 83, NO. 1 



postrostral carina. The complex intergradation of 

 the characters that have been used to recognize 

 these "Divisions" and "groups" of Sicyonia seems 

 to demonstrate that there are no superspecific dis- 

 junctions that will justify their being accorded 

 subgeneric or generic rank. In the present work, 

 occasionally, reference is made to these subdivi- 

 sions. 



Key to the American Pacific species of 

 Sicyonia 



la. First abdominal somite lacking tooth on 

 dorsomedian carina S. mixta 



lb. First abdominal somite bearing anterior 

 tooth on dorsomedian carina 2 



2a. Antennal spine absent or exceedingly 

 weak and without buttress; second abdom- 

 inal somite with perpendicular incision 

 in anterior half of dorsal carina; first 

 pereopod with short distomesial spine on 

 basis and ischium 3 



2b. Antennal spine well developed and but- 

 tressed; second abdominal somite not 

 incised; first pereopod with basis and 

 ischium unarmed 4 



3a. Postrostral carina armed with 3 sub- 

 equal teeth, anterior (epigastric) one as 

 large, or almost as large, as posterior 2 

 teeth; anteromedian sulcus of first abdom- 

 inal somite well marked to near ventral 

 margin of pleuron; posteroventral extrem- 

 ity of fourth abdominal somite dis- 

 tinctly angular S. disparri 



3b. Postrostral carina armed with 3 unequal 

 teeth, anterior one conspicuously smaller 

 than posterior 2 teeth; anteromedian sul- 

 cus of first abdominal somite short, often 

 obscure, ending well above ventral mar- 

 gin of pleuron; posteroventral extremity 

 of fourth abdominal somite never distinct- 

 ly angular S. laevigata 



4a. Postrostral carina with 2 or 3 teeth pos- 

 terior to level of hepatic spine 5 



4b. Postrostral carina with 1 tooth posterior 

 to level of hepatic spine 7 



5a. Postrostral carina almost always with 3 

 teeth posterior to level of hepatic spine, 

 occasionally anterior one of these at level 



of or slightly anterior to hepatic spine 



S. brevirostris 



5b. Postrostral carina with 2 teeth posterior 

 to level of hepatic spine, never with tooth 

 at level or slightly anterior to hepatic 

 spine 6 



6a. Rostrum bearing 2 dorsal teeth; 

 petasma with distal projections short and 

 stout; thelycum with plate of sternite XIV 

 raised in low (sometimes indistinct) 

 bulges and with posterior component of 

 median plate traversed by weak suture; 

 branchiostegite with large ocellus consist- 

 ing of well-defined yellow center sur- 

 rounded by purplish brown ring 



S. disedwardsi 



6b. Rostrum usually bearing 1 dorsal tooth 

 (rarely 2); petasma with distal projections 

 extremely long and slender; thelycum 

 with plate of sternite XIV raised in strong 

 bulges and with posterior component of 

 median plate traversed by deep groove; 

 branchiostegite with moderately large, 

 purplish brown spot sometimes bearing 

 poorly defined but diffuse yellow center 

 S. penicillata 



7a. Postrostral carina behind posterior tooth 

 high, conspicuously elevated in arched 

 crest 8 



7b. Postrostral carina behind posterior tooth 

 low, not elevated in high crest 11 



8a. Fifth abdominal somite without tooth or 

 sharp angle at posterior end of dorsome- 

 dian carina; anteroventral extremity of 

 pleuron of fourth abdominal somite broad- 

 ly obtuse and unarmed S. affinis 



8b. Fifth abdominal somite with tooth or 

 sharp angle at posterior end of dorsome- 

 dian carina; anteroventral extremity of 

 pleuron of fourth abdominal somite sharp- 

 ly angular or armed with spine 9 



9a. Rostrum long, conspicuously surpassing 

 distal margin of eye; anteroventral angle 

 of second through fourth abdominal 

 somites unarmed, lacking spine; petasma 

 with projection of dorsolateral lobule dis- 

 tinctly bifurcate apically S. martini 



9b. Rostrum short, falling short of, or infre- 

 quently barely surpassing distal margin 

 of eye; anteroventral angle of second 



10 



