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



proximatus. The chief distinctive feature, however, exists in the very decided difference, 

 both in position and character, of the armature on the frontal crest posterior to the orbits, 

 and which consists of ten small movable spinules closely planted together, from that on 

 the rostrum anterior to the orbits, which consist of eight low-lying fixed teeth, that are 

 placed widely apart. The portion of the rostrum which was broken off has been found, 

 so that its length can be accurately determined to be over two-thirds the length of the 

 carapace, or a little longer than the scaphocerite, and it gradually narrows from the base 

 to the extremity. On the under side of the rostrum there are not any very conspicuous 

 teeth, but five small points can be determined by close observation amidst a fringe of hairs. 



The branchial region is defined by fossae from the cardiac and hepatic regions, and 

 the latter from the gastric and frontal. 



The third somite of the pleon is dorsally produced to a point that reaches, when the 

 animal is extended, to about two-thirds the leugth of the succeeding somite. 



Observations. — The specimen is too much damaged to enable me to describe any 

 other important distinctions from closely allied species, such as Nematocarcinus lanceopes, 

 Nematocarcinus proximatus, and Nematocarcinus longirostris. 



This species may be at once recognised by the number and position of the frontal 

 teeth, and by the shortness of the telson, which does not quite equal the length of the 

 inner branch of the sixth pleopod, and is considerably shorter than the outer, the apex 

 beino' on a level with the diaeresis. 



Nematocarcinus productus, n. sp. (PI. CXXXII. fig. 5). 



Eostrum about half the length of the carapace, anteriorly elevated and gradually 

 tapering ; upper or dorsal margin armed with eighteen or nineteen teeth, of which 

 those on the frontal crest are the more closely placed, while those towards the distal 

 extremity of the rostrum are more separated ; lower margin smooth and fringed with 

 closely packed cilia. 



Third somite of the pleon dorsally arcuate and posteriorly produced so as to cover 

 half the fourth somite, when the pleon is fully extended ; posterior three somites obtusely 

 carinated dorsally. 



Telson long, narrow, and tapering posteriorly to a truncated apex which is furnished 

 with three or four long stiff hairs or spines. 



