364 THE PLANKTON OF THE FAKOE CHANNEL AND SHETLANDS. 



^GISTHUS ATLANTlcus, nov. s]). (One specimen only, which I found in 

 Dr. Fowler's llesearch Collection.) 



Size 1'45 mm. Tail setse 5 J times the length of the whole body, 

 and coalescent throughout their course until just at the end. One 

 is a little shorter than the other, and each ends in a peculiar spine, 

 which articulates with the seta, and probably serves to fix the animal 

 in the mud. This animal, unlike any other Copepod, possesses a sixth 

 pair of feet, eacli a simple process with two hairs. The fifth feet 

 are characteristic, long, and consist of only one segment. The inner 

 terminal fan differs from Giesbrecht's species nmcronatus and aculeatiis, 

 arising more proximately than in either of these, and not reaching the 

 end of the terminal fan. The other feet have three-jointed outer and 

 inner branches, and the second basipodite is joined to the first in quite 

 characteristic manner (see Giesbrecht's figures, Fauna und Flora Neapel. 

 PL 49). 



The anterior antennae consist of six joints ; on the upper margin 

 of the second joint is a strong spine proximally bent, and a long 

 peculiar process (sensory ?) on the third joint, and a similar one on 

 the end joint. The maxilla and post, foot jaw agree closely with 

 ^g. mucronatus (Giesbrecht). Of the mandibles only the biting end 

 remains. 



The body of the animal is more or less torpedo-shaped, and the head 

 narrows in front, and is produced into a long stout spine, curved 

 downwards and forwards. The animal bears some resemblance to 

 JEg. nmcronatus, but is little more than half the size, differs in the 

 length and terminations of the tail setse, the presence of a long sensory 

 process on the last joint of tlie anterior antenna, the possession of a 

 three-jointed internal and external branch of the second feet (two- 

 jointed in mucronatus), the disposition of the fan bristles of the fifth 

 feet, the length of the bristles on the sixth feet (longer than imicronatus), 

 the absence of teeth on the posterior edges of Th. 2, 3, and 4. 



^TIDIUS ABMATUS. 



The examples captured by me in the Faroe Channel and round the 

 Shetlands fall into two groups, and further study will probably warrant 

 the differentiation of more than one species. 



A large number of apparently adult specimens attain a size only 

 of 1-65-17 mm., and in these the rostrum is large and strongly 

 chitinised, the anterior antennse reach quite to, or a little beyond, 

 the end of the furca, and the tenth, eleventh, and twelfth segments are 

 proportionately a little larger than in the second species, and more 



