CANC.RO IDE A. 287 



The specimens here referred to, have the posterior lateral tooth 

 nearly twice as long as either of the others, and directed outward, while 

 the others point forward. There are six teeth in all, the anterior 

 notched at top, or subtruncate. The medial region is crossed by two 

 raised lines, rather strongly drawn, the hinder reaching to the poste- 

 rior lateral teeth. The surface of the carapax has a very short downy 

 coating. The hand has five spines above, two on the upper margin 

 (one of them apical), and three parallel on an outer line. The arm 

 has three spines on its anterior margin. The teeth of the front are 

 somewhat triangular, but hardly acute. The hand has two costae 

 across the medial portion of the outer surface, besides a lower one run- 

 ning into the immoveable finger. The left hand is the largest in 

 our specimens. The emargination in the under orbital margin is 

 very narrow. There are three spines on the anterior margin of the 

 arm, but the inner one is quite small, much less than half the size of 

 the next. Length of carapax of a male, eleven and a half lines ; 

 breadth, between tips of larger teeth, seventeen and three-fourths 

 lines; ratio of length to this breadth, 1 : 1*54 ; between tips of next 

 anterior, sixteen lines ; ratio of length to this breadth, 1 : 1*4. 



The species pertains to that division of the genus having the pos- 

 terior tooth larger than the others ; it is unlike the variegatus, Fabr., 

 (De H.), and the anisodon, De H., in the hand having five spines 

 above, and unlike the callianassa, Edw., as the hand is not "herissees 

 d'^pines courtes." 



Chaeybdis ? 



Plate 17, fig. 13 represents a young individual of a species of Cha- 

 rybdis, which we hesitate to characterize from the single specimen. 

 The sketch is enlarged four diameters. The front is strongly arcuate 

 and entire, excepting the median emargination. The antero-lateral 

 margin has five nearly equal teeth. The first basal joint of the outer 

 antennse is short, and the next joint is articulated with it quite near 

 the orbit, though separated from it by a thin process ; there is a thin 

 ridge or crest upon the first joint, just beneath the second. The sur- 

 face of the carapax is naked and granulous. The legs of the second, 

 third, and fourth pairs are long and very slender. Length of carapax, 

 ten and a half lines ; breadth, thirteen and a half lines ; ratio of 

 length to breadth, 1 : 1*3. 



