1898.] PLANKTON OP THE FAEROE CHANNEL. 993 



Prom S. bipunctata it is readily distinguished by the number of 

 teeth in the accessory rows and the proportions of tail to body. 



A row of stout processes is placed on the ventral side of the 

 rows of accessory teeth. These appear to correspond to the 

 " follicoli vestibolari " of Grassi ; but in forming a single row they 

 differ from those which he figures as characterizing S. heocaptera l . 



I have been unable to detect any trace of a " corona cigliata " 

 (Eiechorgan) on the dorsal surface of the head and neck. 



This species 2 appears to be present in both the " cold " and the 

 "warm" areas 3 of the Paeroe Channel, and to be a characteristic 

 component of the " Mesoplankton," i. e. the floating and swimming 

 organisms between a depth of +100 fathoms below the surface 

 and a depth of +100 fathoms from the bottom. 



Horizontal distribution : 61 18' N., 4 21' W., to 59 42' N., 

 7 7' W. 



Vertical distribution : 



Greatest depth warm area Sta. 19 a, 480 to 350 fathoms ; 

 temp. 46 to 47 P. 



Greatest depth cold area Sta. 13 #, 465 to 335 fathoms ; 

 temp. 31 to 33 F. 



Least depth Sta. 13 t, 100 to fathoms ; temp. 48 to 54 P. 



The least depth given above was the only occasion on which it 

 was taken anywhere near the surface, except for one doubtful and 

 broken specimen at the surface at midnight (Sta. 15). There is 

 no doubt that this species is essentially Mesoplanktonic, with a 

 very wide temperature range (at least 33 to 48 P.) ; it occurred 

 in every haul, but one, of those made between 530 and 100 fathoms 

 (i. e. in eight out of nine hauls) ; it occurred in every haul which 

 began at or lower than 300 fathoms and finished at the surface 

 (three hauls) ; and was taken, certainly, only once in a haul 

 which began at 1 00 fathoms and ended at the surface (once out of 

 twenty-two hauls). 



SPADELLA (KBOHNIA) HAMATA, Mobius. (Plate L. fig. 4.) 



Having obtained a large number of well-preserved specimens of 

 this species, I think it worth while to give an outline (fig. 4) of 

 the external form, since both the original figure of Mobius 4 (which 

 has been simply copied by.Hertwig 5 and by Grassi 6 ) and also the 



1 Grassi, loc. cit. infra, pi. iii. fig. 6. 



2 I am anxious to leave the discussion of the bathymetric limits of the species 

 taken on H.M.S. ' Research,' and of the means used to determine these limit?, 

 till the material has been more fully investigated. At, the same time, in 

 describing a new species it is necessary to provisionally indicate the depth fct 

 which it was taken ; but remarks under this heading must be for the present 

 considered as provisional, except in the case of surface forms. 



3 For an explanation of these areas, see Wyville Thomson, ' Depths of the 

 Sea.' London, 1874. 8vo. 



4 Jahresb. Commiss. wissenschaft. Untersuch. deutschen Meere, Jahrg. ii., 

 iii. p. 158, pi. iii. fig. 13. 



5 " Die Chaetognathen," Jenaische Zeitschrift, xiv. pi. ix. fig. 7. 



6 " I Chetognati," Fauna und Flora Golf. Neapel, v. pi. i. fig. 5. 



64* 



