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



The pleopoda in all except the first pair consists of two long, narrow, flat branches, of 

 equal length and fringed with ciliated hairs ; to the inner side of the anterior branch is 

 attached a long stylamblys, whereas in the first pair of the male the inner branch is 

 reduced to a small, rudimentary, membranous plate. 



Geographical Distribution. — The range of this genus is extensive in area and variable 

 in depth. In the West Indies it was taken by Professor Agassiz off Grenada, at a depth 

 of 626 fathoms, and in the Sea of Antilles at a depth of 955 fathoms. The several 

 specimens in the Challenger collection were taken at depths varying from 2150 fathoms 

 to about 500, but it appears to me that Notostomus must be considered to be a deep-sea 

 form, inasmuch as those localities in which it was got in a depth less than 1000 fathoms 

 were in the vicinity of deeper water. On the southern coast of Japan, where Notostomus 

 japonicus was taken, the station was on the verge of the 1000-fathoms line, beyond 

 which the water rapidly deepens to 2000 and 3000 fathoms. So again on the eastern 

 coast of South America, the soundings north and south show that the Atlantic in this 

 region deepens very rapidly to 1000 and 2000 fathoms. In the Sea of Banda and off the 

 Island of Celebes, specimens were brought up from a depth of 1425 fathoms and 2150 

 fathoms respectively. 



The range in area of this genus is very great and almost cosmopolitan. It has been 

 taken in the Atlantic among the West Indian Islands, off the eastern coast of South 

 America, and in the middle of that ocean as far south as Tristan da Cunha. In the east 

 it has been taken in the sea south of New Guinea, along the coast of Celebes, and as far 

 north as Japan. 



Notostomus patentissimus, n. sp. (PI. CXXXIII.; PI. CXXXIV. figs. 1, 2). 



Carapace arcuate, dorsally carinated from the posterior margin to the rostrum, 

 which is short, and horizontally straight. The lateral walls of the carapace are traversed 

 on each side by five longitudinal carina?, three of which extend from the frontal to the 

 posterior margin, and the other two commence at the anterior margin of the branchial 

 region and terminate in the posterior margin of the carapace. 



Pleon arched and dorsally carinated ; first two somites carinated but not dentate, 

 the four following all carinated and posteriorly produced to a strong dorsal tooth. 



Telson laterally compressed, dorsally grooved, and subequal with the inner, but not 

 so long as the outer, plates of the rhipidura. 



Ophthalmopoda pyriform. 



First pair of antennae about as long as the carapace. 



Second pair of antennae about as long again as the animal and carrying a scaphocerite 

 that is broader at the base than at the distal extremity, which reaches considerably 

 beyond the apex of the rostrum, and is armed on the outer margin with a conspicuous 

 tooth. 



