Mr. Lubbock on some Arctic species of Calanidse. 1 25 



XIII. — On some Arctic Species o/" Calanidse. 

 By John Lubbock, Esq., F.Z.S. 



[With a Plate.'y^^"^ ^' 



Among the Crustacea collected by Dr. Sutherland in the Arctic 

 Ocean, during the late cruise of the Isabel, commanded by 

 Captain Inglefield, are the following species of Entomostraca : — 

 Arpacticus um?'emis, Gaimard ? ; Anomalocera Patersonii, Tem- 

 pleton ; Calanus arcticus, Baird; C. magnus, n. s.; C borealis, n.s.; 

 C. plumosus, n. s.; C. elegans, n. s. ; C. longus, n. s. 



Gaimard has figured, but not yet described, the above-men- 

 tioned Aipacticus, so I do not feel quite sure about the species. 



Unluckily I have not been able to find the eyes in any of these 

 species of Calanus, for the spirits of wine seem to have removed 

 all traces of them. Considering that C. arcticus was the only 

 one as yet described from that part of the world, the large pro- 

 portion of new species is not surprising. 



Calanus magnus, n. s. Frons rotundatus. Cephalothorax mag- 

 nus, 6-articulatus, postice rotundatus, in medio acutus. An- 

 tennae anticse corpore paulo longiores, setis longis. Abdomen 

 4-articulatum, stylis brevibus. Pedes biremes primi, ramis 

 3-articulatis ; quinti ramis 2-articulatis. 



Long. I unc. 



Hab. Mare Arct. N. Lat. 76° 10'-77°, W. Long. 60'^ 6'-7 F 37'. 



This species may at once be distinguished from all Dana's 

 species, both of Calanus and Rhincalanus, by having 6 cephalotho- 

 racic and 4 abdominal segments, long antennary setse, and the 

 4 posterior cephalothoracic segments of unequal size. The spe- 

 cies figured by Gaimard in his ' Voyage en Scandinavie ' all have 

 the cephalothorax rounded behind, and in Cetochilus sejjtentrio' 

 nalis the head forms a distinct segment. The general shape of 

 the cephalothorax seen from the side is a long ellipse, the second 

 segment being the broadest part. The anterior segment is much 

 the largest, then the second, and after that the others gradually 

 decrease in length as well as in breadth. The posterior is 

 rounded and obtusely pointed in the centre. It is the largest 

 s})ecies of Calanus that I know. 



The anterior antennce are a little longer than the body, and 

 about 24-jointed. The fourth segment, counting from the apex, 

 has a small hair on each side at the apex. The third has two 

 small ones on the anterior, one of which as usual is lanceolate, 

 and one long one on the posterior side at the apex. The second 

 has a long one on each side, that at the posterior being however 

 the largest. The apical segment bears several rather long hairs. 



