296 Dr. J. Vosseler on the 
and in this I have been aided by the kindness of Prof. Jules 
Richard, of Paris, to whom I am indebted for correctly deter- 
mined specimens of this species, which would be difficult to 
recognize from Lilljeborg’s description. 
The slender ovate thorax is not strikingly distinguished 
from the short abdomen. The lateral angles of the fourth 
segment are not produced. The first antenne extend the 
whole length of the body and are very strongly constructed, 
by no means slender. Lilljeborg’s statements as to the geni- 
culate male antenne, namely “ articulus antepenultimus plane 
dearmatus,” I do not find to be correct. In my investiga- 
tions I always found seated upon the joint in question two 
setee, one of which is very long. 
The following numbers show the comparative lengths of 
the individual joints in the female antennee :— 
1, 3% i, iV. Vv. Vi. VE. “VIEL Ox. 0X. Xi. X0L. bee kee 
B02 207 15. 1218. 18. 200) 18s [18.718 20) US.) 255: 
SV. VE.) UNVEIL, XVI TKS OK KT, SE | (eee eae 
205.20; 26, 28. BO Dan yao Os 35. Co eee! 
The mandibles are armed with six distinct teeth, besides 
which there are towards the emargination some rudimentary 
ones. ‘The inferior maxilliped is more stumpy than in D. 
gracilis, Sars. Its first jomt has, on the anterior margin, 
four ridges, of which the first bears one seta. On the second 
there are two, on the third three, of which the middle one is 
the shortest, and on the fourth four sete. One of the most 
important characters of this species, as in the other species of 
the genus Diaptomus, is furnished by the structure of the 
rudimentary pair of feet. The rudimentary foot of the female 
consists of a short basal joint upon which are seated a two- 
jointed outer and a one-jointed imner ramus. The first joint 
ot the outer branch is long; the second cleft at the apex into 
two dissimilar parts. Of these the inner one forms a spine 
bent inwards; the tip of the other bears a short and a long 
seta, the latter extending as far as the end of the above- 
mentioned spine. Opposite the base of the spine on the outer 
side of the joint there is a fine setule. The inner ramus is 
longer than the first joint of the outer one and furnished at 
the end with two sete of nearly equal length, besides which 
there is a smaller one seated more towards the inner side. 
The right rudimentary foot of the male consists of a basal 
joint which is but little longer than broad. The first joint of 
the outer ramus is short and produced into a small projection 
on the outer margin. ‘The second joint is about as long as 
