1898.] fLAfTKlTON OF THE PABEOE CHATS-NEL. 549 



it is not a little suggestive that the ahove four species (to which 

 may perhaps be added Euchceta hessii and Oandace truncata), which 

 appear to have wandered north of their usual habitat, were only 

 taken in the 'Eesearch' from the Mesoplankton, and iu all cases 

 marked by Mr. Thompson as "Scarce." All six occurred once 

 only, except Euchceta marina, which was captured twdce. It seems 

 at any rate possible that these wanderers had either been killed by 

 a reduced temperature, or at any rate so numbed by cold as to be 

 gradually sinking to the bottom. 



Acartia clausii of Giesbrecht has been separated by that author 

 from A. (Bias) longiremis of Lilljeborg ; he uses the latter specific 

 name for species from the Baltic and Sound only. Assuming his 

 view to be correct, the area of A. clausii has been somewhat ex- 

 tended northwards by the 'Eesearch' collections: it reaches south- 

 wards to the Canary Islands, including the Meditei-ranean. 1 

 gather, however, froin Mr. Thompson that he himself would prefer 

 to regard the Baltic and North Atlantic forms as varieties of one 

 species. 



A. clausii appears to have been known hitherto as an epiplank- 

 tonic form only \ Possibly its occurrence in deep water, at Station 

 20, may be due to dead or numbed specimens sinking from the 

 surface ; but it was so regular in its appearance on that occasion 

 (in three out of four mesoplaukton liauls), that, if the above 

 explanation be correct, a very large swarm of this species must 

 have succumbed to cold recently. As it did not occur in my meso- 

 plankton hauls in 1896, I should prefer to leave the question 

 open. 



Rhincalanus cornutus and Aetidius armatus have been sparingly 

 recorded from both Atlantic and Pacific Oceans, but not, so far as 

 I know, from as far north as the Paeroe Channel. 



As regards the remaining species in Mr. Thompson's list, there 

 does not appear to be anything of mark connected with their 

 appearance in the ' Eesearch ' collections, with the exception of 

 Argnlus (cf. p. 544). 



The following conclusions as to vertical distribution appear to 

 be justifiable on a comparison of the ' Eesearch' collections with 

 other records : — 



Oalanus finmarchicus is eurythermal and eurybathic. 



Metridia armata and Euchceta norvegica, two essentially Arctic 

 types, tend to descend to the Mesoplaukton on reaching lower 

 latitudes. 



Eucalanus attenuatus and Pleuromma ahdominale are apparently 

 eurythermal and eurybathic. 



Temora longicornis and Anomalocera patersoni are apparently 

 confined to the Epiplankton. 



1 F. Dahl, Verhancll. deutschen zool. Gesellsch. 1894, p. 64. 



