REPORT ON THE CRUSTACEA MACRURA. 439 



The first pair of antennae has the peduncle rather longer than the rostrum, having 

 the first joint long and the two following short, terminating in two flagella, of which the 

 inner is short and uniarticulate, and the outer stout, but in the specimen it is broken at 

 the first articulus. The base of the first joint of the peduncle is broad and flat, furnished 

 on the outer margin with a strongly projecting point; within this space is an otocyst 

 containing a spherical otolith. 



The second pair of antennae is broken off at the extremity of the peduncle, which is 

 short, stout, and carries a scaphocerite that is long, narrow at the base, and increasing in 

 width towards the extremity, armed with a tooth on the outer side and foliaceous on the 

 inner, which is furnished with cilia. 



The mandibles are not furnished with a synaphipod. 



The first pair of gnathopoda is like that of Sergestes, but the terminal joint is rather 

 cylindrical than spatuliform, but this may be the result of its immature condition. 



The other appendages of the pereion are broken off, so that I cannot determine their 

 form, nor can I determine the presence of the last two pairs of pereiopoda. The first 

 somite of the pleon is furnished on each side with a projecting process that is homologous 

 to the pleocleis of larger species. 



The pleopoda are all long and single-branched, all but the first pair having a small 

 bud-like process, which is the rudiment of the inner ramus, at the distal extremity of the 

 basal joint; these are small on the second pair, and gradually increase in size posteriorly. 

 The sixth or terminal pair, which forms the outer plates of the rhipidura, has the basal 

 joint armed on the outer distal angle with a short robust tooth. The outer plate is a 

 little longer than the telson, and is armed on the outer margin with a long tooth about 

 one-third distant from the apical extremity; the inner branch is narrow and tapering, 

 about the length of the telson, and fringed on both sides with long delicate hairs. 

 Length, 4 mm. (0'17 in.). 

 Habitat. — North of New Guinea. 



Observations. — The absence of the posterior two pairs of pereiopoda is suggestive of 

 its relation to the genus Acetes ; but the specimen is undoubtedly that of an animal not 

 fully grown. The ocellus is still visible as a small longitudinal black streak. The rostrum 

 is slender, and has a deciduous appearance from its delicate, thin, dermal covering. This 

 is also the condition of the terminal appendages of the telson, and the general structure 

 is that of an animal that has not arrived at its mature condition, but is approaching it, 

 although its dimensions are still small. 



The second stage represented on PI. LXXVIII. fig. 2, is in the Mastigopus condition, 

 and is more perfectly preserved than the preceding. 



The carapace is nearly as long as the pleon, excluding the telson. Eostrum broken. 

 Dorsal surface armed with a tooth on each side corresponding with the extremity of the 



