112 RATHBUN 



nearly as far as, or farther than, the spine. 

 Hands a little over twice as long as wide 



nigricauda. 



H'. Antero-internal angle of scale is not produced, and 

 the spine reaches much beyond the blade. 

 Hands two and a half to three times as long as 

 wide. 



J. Scale shorter than the carapace, exclusive of ros- 

 trum alaskensis. 



]'. Scale as long as the carapace, exclusive of 



rostrum alaskensis elongata. 



E'. Sixth segment of abdomen convex, not sulcate, beneath. 

 F. Hands very stout, only two and a fourth times as long 

 as wide ; antepenult segment of outer maxillipeds 



greatly dilated alba. 



F'. Hands elongate, about three and a half times as long as 

 wide ; antepenult segment of outer maxillipeds not 



dilated holmesi. 



C'. Carapace with 2 median spines. 



D. Both median spines in front of the middle of the carapace. 

 E. Rostrum slightly ascending, rounded at the tip. Surface 



pubescent commnnis. 



E'. Rostrum ascending at an angle of 45 degrees, tip pointed. 

 Surface naked. 



F. Eyes of moderate size resima. 



F'. Eyes very large abyssomm. 



D'. Posterior of the median spines situated at about the middle 



of the carapace intermedia. 



B'. Carapace without a median gastric spine .... stylirostris. 

 A'. Gastric region depressed below the general level of the carapace. 

 B. Second lateral carina of the carapace (counting from the middle) 



unarmed. 

 C. Rostrum not spiniform, extremity obtuse. 



D. First to fourth abdominal segments, inclusive, smooth. 



E. Anterior median spine not advanced so far as the line of 



the orbits munita. 



E'. Anterior median spine projecting in front of the line of the 



orbits acclivis. 



D'. First to fourth abdominal segments more or less carinated. 

 E. First to third segments of the pleon armed laterally with 



2 spines each spinosissima. 



E'. First to third segments of pleon unarmed . . variabilis, 



C'. Rostrum spiniform, sharp spinirostris. 



B'. Second lateral carina of the carapace armed with a spine a little 

 behind the superior lateral spine munitella. 



CRANGON NIGRICAUDA Stimpson. 



Crangon nigricauda STIMPSON, Proc. Calif. Acad. Sci., I, 97, 1856; Jour. 

 Boston Soc. Nat, Hist., VI, 496, pi. xxn, fig. 6, 1857. 



