COPEPODA.—BRADY. 15 
are examples which may fairly be referred to the same species. They are at once 
distinguishable from QO. finmarchicus and C. propinquus by the absence of spinous 
armature on the basiopodites of the fifth pair of feet. I have noticed also that in some 
cases both branches of the fifth pair are only bi-articulate, and I find a similar state 
of things in some of the “ Challenger ” specimens—possibly a character of immaturity. 
But since the foregoing paragraph was written I have received from my old friend and 
pupil, Miss Marie V. Lebour, an extremely interesting paper on the life history of Calanus 
finmarchicus, which entirely confirms my suspicions of immaturity of the bi-articulate 
fifth pair of feet. The research on the development of this Calanus was begun by 
Mr. L. R. Crawshay in the Plymouth Laboratory, and completed by Miss Lebour after 
the original author had left for the war. It embraces a complete account of the 
development of all the limbs and appendages from the nauplius stage onwards, and 
finally sets at rest any doubt as to the meaning of the bi-articulate fifth foot.* The 
form described by Dr. Giesbrecht in his ‘* Belgica’ report, under the specific name 
acutus, may perhaps belong to the present species, The stations in which C, tonsus 
occurred are as follows :— 
Stations 1, 2, 7, 8, 9, 12. 
Genus DIARTHROPUS gen. nov. 
Four pairs of feet in the female, five in the male; exopodite and endopodite 
uniformly bi-articulate, except as to the fifth pair of the male, both branches of which 
are one-jointed. Abdomen of the male three-jointed; of the female two-jointed, 
DIARTHROPUS TORTICORNIS sp. nov. 
(Plate VJ, figs. 11-19.) 
Length, 1-6 mm. Anterior antenne twenty-four jointed, stout, almost without 
marginal sete, except the three terminal joints, each of which bears a long hair. The 
antennx, in all the full-grown specimens which I have seen, are bent so as to form a 
sub-circular loop, the apical joints coming almost in contact with the base of the limb. 
There are two frontal tentacular filaments. Mandibular palp small, consisting of a 
rather bulky base from which arise two short branches, of one and two joints respectively. 
Both branches of the first four pairs of feet are bi-articulate; those of the fifth pair in 
the male consist of one joint only. 
Only few specimens of this species were found, but among the profusion of small fry, 
from which they are not readily distinguishable, doubtless more are to be detected by 
careful search. The only localities in which they were found are Station 2, off Maria 
Island, Tasmania, and Station 6, off Macquarie Island. 
*Stages in the Life History of Calants finmarchicus (Gunnerus), Reared by Mr. L, R. Crawshay in the Plymouth 
Laboratory, by Marie V, Lebour, M.Sc, 
