432 THE VOYAGE OF H.M.S. CHALLENGER. 



near the base with a strong sharp tooth. The third pair of pereiopoda is minutely 

 chelate. The fourth and fifth pairs are rudimentary, the anterior being slightly jointed 

 and the posterior in a state of gemmation. 



The pleopoda are long and fairly robust, and have both branches far advanced in 

 development. The posterior pair has the inner plate twice as long as the telson, and 

 the outer three times as long, fringed on each side with hairs, those on the inner side 

 long, on the outer short ; it is not armed with a tooth at any point. 



Length, 7 mm. (0'28 in.). 



Habitat. — North of the Sandwich Islands. 



Observations. — This species corresponds very closely with Sergestes nasidentatus. 

 from which it differs in having the eyes much larger in diameter and more fungiform, 

 but especially in having the median ventral surface of the three anterior somites produced 

 to prominent lobes, surmounted by a strong tooth directed obliquely forwards. It differs 

 also from Sergestes spiniventralis , which has the five anterior somites of the pleon 

 similarly armed ventrally, but has every somite except the first dorsally furnished 

 with a strong tooth, while in this species the dorsal surface is smooth throughout, except- 

 ing for a small point at the posterior extremity of the sixth somite, as in Sergestes 

 nasidentatus, and it has the posterior pair of pleopoda smooth, whereas in Sergestes 

 nasidentatus the outer margin is armed with a strong tooth. Sergestes ventridentatus 

 was taken in Mid-Pacific, north of the Sandwich Islands, while Sergestes spiniventralis 

 was found in the western part of the same ocean, and Sergestes nasidentatus was taken 

 about 800 miles off the coast of Chili, at a depth of 200 fathoms. 



Sergestes brachyorrhos, Kroyer. 



Sergestes brachyorrhos, Kroyer, Monograph. Fremstilling af Kraeb. Sergestes, pp. 56, 65, Tab. v. 

 fig. 13, a, b. 



" Rostrum distinctly prominent, very acute, and reaching to half the length of the 

 ophthalmopoda. Ophthalmopoda very large, reaching to the extremity of the second 

 joint of the peduncle of the first pair of antennae, broadly clavate or subfungiform ; 

 ophthalmus very distinct from the peduncle, in breadth equalling half the length of the 

 ophthalmopod, and in length scarcely a third of it. 



" First pair of antennae having the peduncle nearly one-fourth of the length of the 

 animal, or more than two-thirds of that of the carapace. The first joint nearly equals 

 the second and third combined, and is twice as long as the third. 



" Second pair of antennae having the scaphocerite more than four times longer than 

 the last joint of the peduncle, and reaching to the extremity of the peduncle of the first 

 pair of antennae. 



