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



Length, G mm. (0 - 25 in.). 



Habitat. — Mid Atlantic, April 1876. 



Observations. — The specimen has the appearance of being an immature animal, and 

 but for the form of the ophthalmus and the length of the rostrum I should have thought 

 it related to Sergestes ancylops ; it is about twice its size, and differs in some other 

 apparently important features. 



Sergestes junceus, n. sp. (PI. LXXVI. fig. 1). 



Rostrum small and slightly elevated above the dorsal surface of the carapace, which 

 is a little less than half the length of the animal exclusive of the telson. 



Pleon with the first three somites subequal and dorsally smooth. The two suc- 

 ceeding subequal in length, and dorsally armed with an elevated tooth just in front of 

 the posterior margin. Sixth somite rather longer than the three preceding combined, 

 posteriorly produced to a small tooth, and with the lateral walls not deeper than those of 

 the preceding somites. 



Telson nearly half the length of the sixth somite. 



Ophthalmopoda about one-third the length of the carapace, and reaching a little 

 beyond the distal extremity of the first joint of the first pair of antennas. The 

 ophthalmus is not very large, and the stalk, which is slender, narrows at first suddenly, 

 and then gradually to the base. 



The first pair of antennae is about half the length of the carapace ; the first joint is 

 longer than the other two, and reaches nearly to the extremity of the ophthalmopod ; 

 the second is about one-third the length of the first, and the third is shorter than tin- 

 second, and supports a flagellum, which is broken, and a short rudimentary appendage. 



The second pair of antennae carries a long, narrow scaphocerite, which is armed on 

 the outer margin at a little distance from the extremity with a lono- and slender tooth ; 

 the inner margin is fringed with ciliated hairs. 



The oral apparatus is situated anterior to the centre of the carapace. 



The first pair of gnathopoda is rather slender, and is only generic in character. The 

 second pair is wanting, but the coxa is larger in diameter than that of the other limbs. 



The first pair of pereiopoda is long and slender, and devoid of any prehensile 

 apparatus. The second pair is long and slender, and is once and a half as long as the 

 first pair, and terminates in a very minute chela. The third pair is broken off at the 

 basis. The fourth and fifth pairs are merely rudimentary or bud-like. 



The pleoj^oda are long and slender, slightly decreasing in length, and increasing much 

 in diameter posteriorly. The posterior pair, which forms the outer plates of the rhipidura, 

 is long and broad, about as long as the sixth somite of the pleon ; the outer margin of 



