132 NOTES ON THE COPEPODA OF THE 



In addition there are minor differences in the relative proportions of 

 the segments of the feet, number of teeth on the terminal saws, hooked 

 bristles of the anterior foot-jaws, proportions and length of the segments 

 of the posterior foot-jaws (first and second basals shorter and broader). 



The differences, though small, along with the widely different habitats, 

 cause me to hesitate before regarding them as identical, and probably 

 they are varieties, 



Gaetanus. Of the two species of Gaetanus (armiger and major) which 

 I find common in the Atlantic, and somewhat more uncommon in the 

 Faroe Channel, the doubt may be expressed (as in the case of Gaidius) 

 whether the species G. armiger is really identical with Giesbrecht's 

 Pacific Ocean examples. Specimens from the Atlantic clearly have 

 the modified tubal bristles on the basal of the fourth feet (apparently 

 absent in Giesbrecht's species), and are larger than Giesbrecht's species 

 (viz. 4-4 mm., as compared with 3-2 mm.), but otherwise the resemblance 

 is very great. However, combined with such widely different habitat, 

 it might be considered advisable to regard them as different species, in 

 which case our northern species might be distinguished as G. ailanticus. 

 No doubt can be entertained in the case of Gaetanus caudani that it is 

 not identical with G. miles (Gbt.), though doubt may be felt whether 

 the specimen described by Canu {Ann. Univ. Lyon, vol. xxvi.) is identical 

 with the North Atlantic examples ; but as this appears to have been an 

 immature male, a proper comparison can scarcely be made. 



With regard to the horizontal distribution of the genera Gaidius and 

 Gaetanus, Gaidius is of constant occurrence in the deep water only of 

 the Faroe Channel, and though it wanders south into the warm Atlantic, 

 it is by no means of such frequent occurrence as further north. Gaidius 

 major, and to a less degree G. 'puwjens, are in the North Atlantic 

 distinctly boreal species, occurring with frequency in the Polar seas 

 (Sars). Chiridius obtusifrons seems at present to be still more markedly 

 a Polar species, occurring sparingly in the cold under- water of the Faroe 

 Channel, and Fseudwtideus armcdus has the same distribution as Gaidius. 

 Both can be traced down as far as lat. 51° N., possibly further south. 



Gaetanus species, on the contrary, appear to be of more a warm 

 Atlantic area habitat. Their frequency diminishes going northwards, 

 and Gaetanus is not mentioned in Sars' lists. G. major alone passes 

 into the Faroe Channel, 0. armiger and caudani not appearing north 

 of the Wyville-Thompson ridge, though on one occasion I took an un- 

 developed example (? G. miles vel caudani) just south of this locality. 



Eucliceta. E. marina, described in Fowler's paper as common at 

 various depths, is erroneous.* It does not occur in the Faroe Channel, 

 nor have I found it in the North Atlantic, at any rate as far south as 

 * Its inclusion in my list (tliis Journal, January, 1902) was also an error. 



