158 STALK-EYED CRUSTACEA. 



Nematocarcinus agassizii Fax. 



Plate XLII. 

 Bull. Mas. Comp. ZooL, XXIV. 204, 1893. 



The rostrum is one fifth longer than the rest of the carapace (in some small 

 specimens only equal to the rest of the carapace), slender, nearl}^ horizontal 

 for the basal two fifths of its length, the remaining portion gently upturned 

 and ending in a very acute point ; its upper margin is continued backward 

 in the form of a carina, which becomes obsolete on the hinder part of the 

 "Mstric region ; this carina is pectinate, or armed with close-set, foi'ward- 

 pointing teeth on the anterior part of the gastric region, and the teeth are 

 continued on the upper margin of the rostrum through one third or two 

 fifths of its length, the distal third or three fifths of the rostrum being 

 entirely free from teeth above ; the lower edge of the rostrum is ciliated 

 above the eyes and armed with three (rarely four) teeth, separated by wide 

 intervals, on the distal half. 



The third abdominal segment is somewhat prolonged posteriorly over the 

 next segment, but the hind margin is rounded off and does not form a promi- 

 nent tooth. The telson is tipped with three pairs of spines, the intermediate 

 pair the longest ; there are, besides, about six pairs of small spines on the 

 dorsal side of the telson. 



The flagella of both the antennules and antennae are prodigiously de- 

 veloped, the antennule being nearly twice, the antenna more than twice the 

 length of the whole body including the rostrum; excepting the proximal part 

 of the organ, the annuli- of the antennal flagellum are enlarged at the distal 

 end, giving a beaded appearance to the fiagellum ; the antennal scale reaches 

 rather more than half-way to the end of the rostrum ; it is truncate at the 

 distal end and armed externally with an apical spine. 



The legs have the characteristic shape and proportions of the genus. The 

 dactyli of the third and fourth pair are slender, acute, somewhat curved, and 

 invested with a pencil of long hairs. The dactyli of the fifth pair are stouter 

 but very .short, and hidden in the tuft of hairs which arises from the distal end 

 of the propodite. 



The outer blade of the swimmeret slightly surpasses the telson. It is 

 fringed with long hairs along the internal and distal margin, and furnished 

 with a minute tootli and a movably articulated spine on the external border 



