THE PLANKTON OF THE FAKoE CHANNEL AND SHETLANDS. 365 



or less coalesced. The pointed angles of the last thoracic segment 

 are also dorsally more prominent and the spurs are shorter than in the 

 other group (in which they reach beyond the end of Ab. 2). 



In the second group the animals are much larger, 2'0-2'3 mm, long, 

 the rostrum is smaller, the angular point of the last thoracic segment 

 longer, and the antennae are shorter, reaching only to the end of the 

 first abdominal segment, and the joints 10, 11, 12 are more clearly 

 segmented. 



The specimens examined agree more closely with Giesbrecht's de- 

 scription than Brady's {Challenger Beport), whose drawings and de- 

 scriptions contain many inaccuracies, Brady gives the size of jEtidms 

 armatus at 2*1 mm., Giesbrecht 1'55-1'9 mm., and the latter speaks 

 of the variabihty in length of the points of Th. 5. These differences 

 may be accounted for by the occurrence of two closely allied species, 

 further discussion of which I defer for another occasion. 



Gaidius boreale, nov. sp. 



Half a dozen specimens captured at 300 fathoms at station A2 exhibited 

 the following characters as described by Giesbrecht {Bull. Mus. Comp. 

 Zool. Harvard, 1895) : Short, one-pointed rostrum ; the last thoracic 

 segment produced into a long and sharp point. The inner branch 

 of the posterior antenna ! outer half : : 5 : 8. The bristles of the 

 inner branch are 8 + 6. The head rounded, and without crest. 

 Abdomen of four segments, the genital segment strongly swollen, but 

 quite symmetrical. Of the swimming feet, the first has a two-jointed 

 exopodite and one-jointed endopodite; the second, third, and fourth 

 have three-jointed exopodites, but while the third and fourth feet have 

 three-jointed endopodites, the second foot has an endopodite with only 

 one joint like the first foot. There is an indistinct trace of segmentation 

 into two joints. 



The maxilla and mandible resembles Gaetanus. In the posterior foot 

 jaw the second basal, which is longer than the first, is about three 

 times as long as the five-jointed endopodite. The fourth feet have the 

 stiff, broad bristles on the inner margin of the second basal, which 

 slightly resembles the lamellae of the same foot of Euchirella rostrata, 

 and of which Giesbrecht remarks, " Die Fiedern am proximalen Theile 

 des Innenrandes des 1 Basalgliedes sind am 4 Fusse breiter, und, 

 wie es scheint, steifer als an den vorhergehenden Fiissen, worin man 

 einen Uebergang zu den Lamellen und Stacheln linden wird, welche 

 sich bei Euchirella an der gleichen Stelle finden " {loc. cit). 



The size of my animals is 3-55 mm. ( $ ), while that of Giesbrecht's 

 is 3 2 mm. The limits of distribution of Giesbrecht's species were 



