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



the lateral walls of the carapace free from carinas, the supraorbital teeth not so long, 

 the fiagellum of the second pair of antennas shorter than the rostrum, and the telson 

 longer than the sixth pair of pleopoda. 



Icotopus, 1 n. gen. 



Carapace dorsally smooth, anteriorly crested, produced to a long rostrum, serrate on 

 the upper and lower margins. Frontal margin furnished with a supraorbital tooth, and 

 with a large fronto-lateral tooth. 



Pleon having the somites subequal ; sixth somite a little longer than the fifth. 



Telson long, tapering, and sharp pointed. 



Ophthalmopoda long, pyriform. 



First pair of antenna? biflagellate. 



Second pair of antennae long and slender, and supporting a foliaceous scaphocerite 

 armed with a tooth at the distal extremity. 



Gnathopoda and pereiopoda formed on the same type, all being simply pediform or 

 not chelate. 



Branchiae as in the following; table : — 



Pleurobranchiae, . . . 1 1 1 1 1 



AithrobranehiaB, . . . 



PodobranchiiC, . . . 



Mastigobranchite, . . . 1 1 



li i k 1 m n o 



Geographical Distribution. — The only species yet known belongs to the Australian 

 seas. 



Icotopus arcurostris, n. sp. (PI. CXLIV. fig. 1). 



Carapace smooth, anteriorly crested, and produced to a long rostrum that is slightly 

 arched, and armed on the upper surface with a series of teeth, and on the lower margin 

 with a few at the distal extremity ; lateral margin fringed with a few teeth posterior to 

 the fronto-lateral angle. 



Pleon dorsally smooth ; telson longer than the sixth somite. 



Ophthalmopoda pyriform, half the length of the rostrum. 



First pair of antennse shorter than the rostrum. 



Second pair of antennae as long as the animal. 



Appendages of the pereion gradually increasing in length posteriorly until the 

 posterior pair, which is not quite so long as the preceding. 



1 EixsVi like ; toSj, foot. 



