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



narrow scaphocerite springs from the second joint and reaches as far as the distal extremity 

 of the ophthalmopod, where, on the outer side, it is subapically armed with a small tooth. 



The first pair of gnathopoda is robust, the terminal joint is ovate and much smaller 

 than the penultimate, which is long, broad, flat and ovate, and the antepenultimate joint 

 is genuflexed near the adjoining articulation. 



The second pair of gnathopoda is very long ; the basis is short and suddenly enlarged 

 to a considerable diameter ; the ischium is much narrower than the basis, but the two 

 next succeeding joints are long, moderately broad, have the margins subparallel and 

 reach as far as the extremity of the ophthalmopod ; the next three succeeding joints 

 narrow to about half the diameter of the preceding, and taper slightly to a blunt apex 

 that has the margins sparsely furnished with a few hairs. 



The first pair of pereiopoda is short, five-jointed, and sparsely fringed with long hairs. 

 The two succeeding pairs are long, slender, and furnished with minute chelae. The 

 penultimate pair is short, saccular and rudimentary, and the last pair is only in a state of 

 gemmation. 



All the pleopoda anterior to the rhipidura have only one branch developed ; at the base 

 of each branch is a small bud-like process that becomes larger on each successive pair. 



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



Habitat. — China Sea, oft' Luzon. One specimen. 



Observations. — Considerable interest is attached to this little species, which I have 

 named in accordance with its apparently intermediate condition, and because it appears 

 to possess features that are in part common to several species. It resembles Sergestes 

 lieviventralis, Sergestes nasidentatus, Sergestes longispinus, and the immature form 

 Mastigopus spin i centralis in the character of the rostrum, which corresponds in relative 

 proportion more nearly with that of Sergestes longispinus than with that of any of the 

 others named. 



It differs from all the preceding species in having a series of large, broad, and longi- 

 tudinally compressed spine-like processes projecting in the median line, one on each of 

 the ventral surfaces of the several somites ; in this, however, it agrees with Mastigopus 

 spiniventralis, as also in the form of the rostrum and in the presence of a small denticle 

 at the postero-dorsal extremity of the carapace ; it also corresponds with it in having no 

 tooth on the outer margin of the outer plate of the rhipidura, in which respect it differs 

 from the other allied species. 



It differs from Sergestes nasidentatus in having a tooth on the dorsal surface of the 

 three posterior somites, and from Sergestes longispinus, Sergestes Iseviventralis, and 

 Mastigopus spiniventralis in having no teeth on the dorsal surface of the anterior three- 

 somites of the pleon. 



Sergestes intermedins has the appearance of being the early stage of an animal that 



