REPORT ON THE CRUSTACEA MACRTJRA. lxxxvii 



These long-legged Prawns (Nematocarcinus) are essentially free-swimming forms, that 

 probably pass their lives in mid-water, at an average depth of 1000 fathoms. The 

 largest number of specimens at the largest number of stations have been taken between 

 500 and 2000 fathoms, while at one station there were fifteen specimens taken at 

 28 fathoms in the shallow waters of the Arafura Sea. In every instance of their capture 

 the trawl was used, although in some instances the dredge was employed also, and it is 

 probable that they only occasionally come into contact with the sea-bottom, and the 

 greatest depth at which they have been taken is 2150 fathoms off the Celebes Islands, 

 or about two miles from the surface. The second deepest range is south of Japan, at a 

 depth of 1875 fathoms, or about one mile and one-eighth. Off Juan Fernandez in the 

 Pacific, specimens were taken at two stations at an average depth of one mile. 



In this genus there are several species which depart from each other in characters 

 apparently so unimportant that it is difficult to fix on any salient points of sufficient 

 importance to determine specific features. Thus Nematocarcinus longicarpus, Nemato- 

 carcinus parvidentdtus, Nematocarcinus paucidentatus, and Nematocarcinus serratus 

 are chiefly determinable by the form and number of the teeth on the rostrum, which 

 bear a relation to one another as to number and position on the upper and lower margin, 

 as shown below : — 



Nematocarcinus parvidentatus, . . Japau, 



„ paucidentatus, . . Fiji, . 



„ serratus, . . New Zealand, . 



„ tenuipes, . . Japan, Admiralty Islands, 



24 





 ^ 



1 

 30 





 20 



1 



Again, if we turn to another group which is remarkable for having a long rostrum, 

 and for being larger when adult, we find that the external variations are but small and 

 apparently unimportant beyond the numerical value of the teeth on the rostrum, which 

 may be tabulated as follows : — 



15 

 2 



26 

 8 



40 

 5 



34 



proximatus, Marion Island, 'Valparaiso, Arafura Sea, Japan, . 



Nematocarcinus altus, . Philippines, 



,, lanceopes, . Antarctic, 



„ lonrjirostris, Japan, . 



These four species have been taken at very distant localities. Nematocarcinus 

 longirostris was found only on the south coast of Japan, Nematocarcinus altus only near 

 the island of Celebes, and Nematocarcinus proximatus at two stations off the western 



