some Entomostraca. 27 



blanches both three-jointed. There is a hair at the apex of the 

 two basal segments of each branch, and the apical segment of the 

 inner branch has two hairs on the margin, and two at the apex ; 

 that of the outer three at the margin, and two at the apex. There 

 are thus five hairs on the apical segment of the outer branch of the 

 fourth pair, while the first pair had four. The addition arises from 

 the development of the spine. 



The fifth pair of legs is long, thin and four-jointed. The basal 

 segment of the larger leg is long and cylindrical ; the second seg- 

 ment is swollen, and gives rise to two branches, which in shape 

 are not unlike the prongs of a pitch-fork, with, however, the 

 power of meeting : the outer branch is two-jointed. The smaller 

 leg is very simple, resembling a rod composed of four pieces, the 

 two basal of which are short, and the two apical long and slender. 



Length -06. 



The abdomen is four-jointed, with the segments subequal ; and 

 tlie caudal stylets small : the second of the caudal setae nearly 

 twice as long as the others. 



Length of cephalothorax '09. 



,, abdomen '03. 



Collected in N. L. 12° 21', W. L. 25°. 



PI. IV. figs. 5 to 8. PI. VIL fig. 6. 



Diaptomus dttbiiis, n. sp. 

 Frons quadrata, Cephalothorax curtus, antice latior, 5-arti- 

 culatus, angulis posticis acutis, segmento primo maximo, tertio 

 quartoque brevibus. Antennae anticae corporis longitudine, 

 setis brevibus ; antenna maris dextra medio paulum incras- 

 sata, fere 24-articulata, articulis 18 et 19 antice serratis, 

 articulis tribus anticis subaequis. Pes posticus maris maxi- 

 mus ad apicem obtusus, rotundatus ; pedes postici foeminae 

 parvi. Abdomen maris 4, foeminse 3-articulatum. 

 There is not a furcate rostrum, but under the front are two 

 little appendages. 



The two branches of the second pair of antennae are nearly 

 equal. The accessory branch has three hairs at the apex, and one 

 at the middle of the apical segment, besides eight along the side, 

 signs of a tendency towards the separation of other intermediate 

 segments over and above the four usual ones. 



The second pair of maxillae and the maxillipeds are formed as 

 in Calanus. 



The first pair of natatories have the two rami respectively three 

 and two-jointed ; and in the fourth pair they are larger, but con- 

 sist of only two and one segments respectively. 



