MUSEUM OF COMPARATIVE ZOOLOGY. 3 



narrower carapax, with much longer rostral horns and fewer and much longer 

 spines. 



The carapax, excluding the rostral horns and lateral spines, is about two 

 thirds as broad as long ; the rostral horns are as long as the breadth of the car- 

 apax excluding the spines, nearly straight, slender, and very acute. There are 

 two spines upon the basal segment of the antenna, but the proximal is much 

 smaller than the distal. The hepatic spine is slender, and about a fourth as 

 long as the rostral horns. There is only one small spine, or one with the rudi- 

 ment of a second, on the margin of the pleural region back of the anterior angle 

 of the buccal area. The two median spines of the gastric region are slender 

 and conspicuous, the posterior much the larger, but there are no lateral spines. 

 The middle spine of the cardiac region is as long as the hepatic, and in front 

 of its base there is a rudiment of a second ; the posteiior cardiac spine is slender 

 and very little shorter than the hepatic, but there are no spines or tubercles 

 either side its base. The middle spine of the branchial region is slender, and 

 more than half as long as the rostral horns ; there is a single small spine in 

 place of the two anterior branchial ; a small posterior branchial is present ; 

 and in place of the series of small spines there are two very minute tubercles. 



The chelipeds and ambulatory legs are nearly as in the other specimen, but 

 the chela; and the dactyli of the ambulatory legs are a little more hairy. 



Station 317, N. Lat. 31° 57', W. Long. 7S° 18' 35", 333 fath. 



The two specimens give the following measurements. 



Station 319 317 



Sex $ Young 



Length of carapax including rostrum and posterior spine 35.2 mm. 13.1 mm. 

 Length of carapax from base of rostrum to tip of pos- 

 terior spine 27.5 8.4 



Length of rostral horns 8.5 5.1 



Breadth of carapax, including lateral spines . . . 27.0 10.5 



" " excluding " " . . 20.3 5.1 



Length of branchial spine 4.5 3.0 



" cheliped 37 8 



" first ambulatory leg 63 16 



" second " 43 13 



Since the above was written several specimens of this species have been taken 

 off Martha's Vineyard by the United States Fish Commission. All these - 

 mens are intermediate in size between those above described, and show that 

 they are really, as supposed, stages of growth of a single species. 



Hyas coarctatus Leach. 



One young specimen, Station 301, N. Lat. 41° 26' 55", W. Lon. 66° 3', 

 71 fath. 



