ISOFODS OF THE ATLANTIC COAST—IIICIIAI'DSOX. 



547 



on the upper lateral margin; the third joint is about three times as 

 long as the second joint, and is armed with two long spines at the 

 upper end; the fourth joint is about twice as long as the third joint, 

 and is armed with a single spine at the upper end; the fifth joint is 

 somewhat longer than the fourth and is unarmed; thetiagellum is long 

 and consists of ten joints. 



The first, second, third, and lifth thoracic segments have each two 

 long projecting spines on either side of the median dorsal line. The 

 fourth, sixth, and seventh segments are without theso spines. The 

 first segment has three spines, one 

 large central spine and two small 

 spines on each anterodateral margin. 

 All the other thoracic segments have 

 one long spine on each lateral margin. 



The first al)dominal segment has 

 one lateral spine on each side; the 

 second segment has two dorsal spines, 

 one on either side of the median line. 

 The third segment has one lateral 

 spine on each side. The terminal 

 segment is rounded in outline posteri- 

 ori}^, with two lateral spines on either 

 side, one a little below the middle and 

 one near the posterior margin of the 

 segment. There is also a large ter- 

 minal spine on the dorsal surface. 



The opercular valves are armed 

 each with a single spine about the 

 center of the valve. The penulti- 

 mate joint of the second, third, and 

 fourth anterior pairs of legs is armed 

 with a single spine. 



One specimen of this species was 

 taken by the U. S. Fish Commission 

 steamer Albatross near Aves Island, 

 Cariljbean Sea. 



T(/pe.— Cat No. 9113, U.S.N.M. 

 This species closelv resembles Ardurus purpxirem Beddard, ditiering 

 from that species in having tw o dorsal spines on the second abdominal 

 segment, spines on the opercular valves, and at the base on the outer 

 margin of the second joint of the peduncle of the second pair of 

 antenna^ in wanting spines on the pi'oximal joints of the anterior 

 thoracic appendages, with the exception of the penultimate joint, and 

 in the greater length of the first pair of antennie. 



Fig 24. — ARf'TURrs caribb^eus. 



