po Addison E. Verrill, 



always present. Lower lateral spine of basicerite (basal antennal 

 spine) slender. Stylocerite, or antennular spine, longer than first 

 segment of antennular stalk. Telson not abruptly narrowed distally; 

 outer lobe of uropods not serrate on margin distally. Smaller chela 

 of first pair of legs without a dense dorsal brush of porrect hairs ; its 

 carpus short. 



C. Frontal spines more or less spiniform, usually longer than wide; 

 rostrum more slender than orbital spines and usually distinctly longer, 

 furnished with a descending vertical process that embraces the ocellary 

 beak Paulsoni-group, 



d. Carpocerite long, at least about 3^2 times as long as wide and exceeding 

 the spine of the scaphocerite; first segment of the carpus of the 

 second pair of legs longer than the remaining four combined. 



e. Basicerite without an upper lateral spine ; telson with acute posterior 

 angles, its inner terminal spines about three times longer than the 

 .outer ones. Rostrum is rather longer than orbital spines, slender, 

 acute, styliform, and equals first antennular segment. . . S. townscndi. 



ee. Basicerite with an upper lateral spine. Orbital spines and rostrum 

 not long; rostrum not longer than orbital spines, acuminate at tip. 

 Inner spine of distal telson angles not more than twice as long as 

 the outer one S. bradlcyi* 



dd. Carpocerite shorter, about one-third as wide as long ; basicerite 

 with an upper secondary spine. Spine of scaphocerite equal to the 

 carpocerite. Large chela stout, with a sharp distal dorsal spine 

 directed somewhat downward 5\ apiocerox* 



CC. Front with three subequal triangular or subacute denticles ; the 

 rostrum similar in size and form to the ocular processes, but it may 

 be a little narrower, or slightly longer or shorter, not styliform. It 

 lacks the inferior vertical prolongation. Telson not rapidly tapered ; 

 distal end broad, convex, with numerous plumose hairs. 



Brevicar pus-group. 



f. Rostrum triangular, similar in form and size to the ocular teeth. 

 Carpocerite cylindrical, slender, at least 4 times as long as wide ; 

 antennal scale 5.5 to 6.4 times as long as wide; basicerite nearly 

 unarmed above ; carpus of legs of second pair 10 to 15 times longer 

 than wide. 



g, Spine of scaphocerite scarcely exceeding the length of the scale. The 

 three frontal processes are short, scarcely spiniform, about as long as 

 width of base, about equilateral, often triangular. Eggs are large and 

 produce Mysls-like larvae S. brevicarpus. 



gg. Lateral spine of scaphocerite is long and slender ; frontal teeth as 

 long as wide ; rostrum has concave margins. Eggs are small ; larvae 

 hatch as Zoea-like forms S. guerini* 



ff. Carpocerite is shorter and swollen, 3.5 to 3.7 times longer than wide; 

 antennal scale longer, from 7 to 8.5 times longer than wide; carpus 



