OP ARTS AND SCIENCES. 123 



the G. Bartonii group, together with the male abdominal appendages 

 of the C. affinis group. These appendages have a projecting shoulder 

 at the base of the rami, on the anterior edge, as in G. rusticus, G. Put- 

 nami, etc. G. immunis and G. Mississippiensis, belonging to the 

 G. affinis group, also have the rostrum devoid of lateral spines, but in 

 general habit of body they do not resemble C. Bartonii and its allies, 

 as is the case with the present species. 



13. C. Mississippiensis, sp. nov. 

 Male, form I. Rostrum broad, twice as long as broad, sub-exca- 

 vated above, smooth, foveolate at base, margins raised, converging 

 anteriorly, sinuate at apex; acumen short, triangular, acute, no lateral 

 teeth. Post-orbital ridges sulcate on outer side, with short, blunt 

 anterior spines. Carapace densely punctate, sides lightly granulate, 

 front lateral border not angulated. Cervical groove sinuate, with 

 small lateral and branchiostegian spines. Areola linear anteriorly to 

 the middle, with a small anterior and a larger posterior, triangular 

 field. Length of areola equal to half the distance from tip of rostrum 

 to cervical groove. Abdomen as long as the carapace. Terminal 

 segment of the telson shorter than the basal segment, hind border 

 slightly concave at the centre ; basal segment bispinose on each 

 side. Anterior angle of epistoma notched. Sternum between the 

 legs densely ciliated. Antennal scale very broad, apical spine short. 

 Third maxillipeds hairy without and beneath. Chelre large, punctate, 

 smooth below, margined without ; inner margin of hand short, fur- 

 nished with dentiform tubercles irregularly disposed in a double series ; 

 a little distance from these is another line of smaller ciliated tubercles 

 on the upper surface of the hand on a line with the middle of the base 

 of the movable finger. Fingers long, gaping at base, each with a 

 punctate impressed line parallel with inner margin, and furnished with 

 rounded tubercles on inner margin. Movable finger tuberculate on 

 outer margin. Outer finger bearded below at base. Carpus broad, 

 obliquely truncate on the external side, punctate and tuberculate above, 

 a strong median internal spine, two small spines near on the base and 

 one at the anterior end near the articulation ; multispinous beneath, 

 the two anterior spines the largest. Meros smooth, two ante-apical 

 spines obliquely placed on upper margin, lower face with blunt biserial 

 spines. Second pair of legs with long setas near the end on inner 

 side, not tufted as in G. immunis. Third pair of legs hooked. First 

 pair of abdominal appendages long, deeply bifid, rami recurved at tip, 

 parallel, internal ramus sub-cylindrical, dilated and grooved at tip, 



