1898.] PLANKTON OP THE FABROB OHANNBL. 993.' 



JTrom S. hipunctata 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. hexaptera '. 



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

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



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

 "warm" areas ^ of the Faeroe 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° F. 



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

 temp. 31° to 33° F. 



Least depth— Sta. 13 i, 100 to fathoms ; temp. 48° to 54° F. 



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° F.) ; 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 tbnn 300 fathoms and liriished at the surface 

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

 which began at 100 fathoms and ended at the surface (once out of 

 twenty-two hauls). 



Spadella (Keohnia) 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 ■* (which 

 has been simply copied by Hertwig ° and by Grassi '') and also the 



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



'■' I am anxious to leave the discussion of the bathymetric limits of (he species 

 taken on H.M.S. ' Eesearch,' and of the means used to determine these limitf, 

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

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

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

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



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

 Sea.' Loudon, 1874. 8vo. 



* Jahrcsb. Commiss. wissenschaft. Untersucli. deutsehen Mecre, Jahrg. ii., 

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



" " Die Ohaetognathen," Jenaische Zeitsckrift, xiv. pi. ix. fig. 7. 



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



64* 



