REPORT ON THE CRUSTACEA MACRURA. 373 



Length, 5 mm. (0'2 in.). 



Habitat.— Station 352, April 13, 1876; lat. 10° 55' N., long. 17' 46' E.; surface 

 temperature, 77° "7. The Atlantic Ocean ; surface. 



Acanthosoma macrotelsonis (PI. LXVI. fig. 1). 



Eesembles Acanthosoma longitelsonis. 



Carapace, without the rostrum, one-third the length of the animal including the telson. 

 Rostrum as long as the carapace, smooth, except for a few points near the extremity. 

 On each side, behind the orbital notch, stands a long, slender, spinous tooth or process, 

 another, which is wide at the base, stands at the antero-lateral angle, and is fringed 

 with long spines and short teeth ; some distance within the margin on the dorsal surface, 

 in a line with or slightly anterior to the mandibles, stands a third but smaller spinous 

 process ; posteriorly and nearer the margin, but at some distance within it, is a 

 fourth small, spinous tooth, while a fifth about the same size projects from a little within 

 the postero-lateral angle. 



The pleon has the five anterior somites subequal in length, and dorsally armed with 

 large, sharp, spinous processes projecting from the median line anterior to the posterior 

 margin; that on the first somite is erect and curved forwards, with the anterior margin 

 smooth and the posterior serrate ; the second is like the first ; the third is straight and 

 armed with one tooth on the anterior margin, and with several on the posterior ; the 

 fourth is straight, pointing oblicpiely upwards and backwards, and armed with teeth on 

 the anterior and posterior margins ; the fifth resembles the fourth in form but is smaller. 

 Each somite is likewise armed at the posterolateral angle with a long, slender, spinous 

 process, of which those on the third and fourth somites are somewhat the longest. 



The sixth somite is as long as the three preceding ; it is dorsally smooth and unarmed, 

 and furnished with a small smooth tooth near the postero-lateral angle. 



The telson is as long as the sixth somite ; it is deeply forked and armed on the 

 lateral margin with three fine, distantly placed teeth. 



The ophthalmopoda are fungiform and about hah the length of the rostrum ; from a 

 slender stalk at the base it increases at first suddenly and then gradually to the 

 ophthalmus, which is nearly twice the diameter of the stalk. 



The first pair of antennas consists of two joints ; the first is long and narrow except 

 at the base, which is considerably enlarged, forming a broad tooth on the outer side for the 

 purpose of enclosing the otocyst. The margins beyond are straight, parallel, and fringed 

 on the inner side with a row of distantly placed hairs. The second joint is short, attached 

 to the first oblicmely, obtusely pointed, and tipped with a few hairs. The first joint 

 probably represents the whole of the future peduncle, and the second the future flagellum. 



The second pair of antennas consists of a basal joint supporting a long and slender 



