430 ]\1ESSRS. T. AXD A. SCOTT — EEVISIOX OF THE BEITISH COPEPODA 



elongate ; outer branches very slender and considerably shorter than the inner branches ; 

 the first joint is nearly equal in length to that of the next two together (PI. 38. 

 figs. 3 and 27). 



Fifth pair small ; apical setfe slender, the middle seta of the secondary joint very long 

 and slender, being considerably longer than the outer elongate and slender seta of the 

 produced part of the basal joint ; a moderately long slender seta springs from near the 

 middle and on the lateral aspect of the secondary joint, — this joint extends very little 

 beyond the end of the produced part of the basal joint (PI. 38. fig. 30). 



Habitat. Off St. INTonans, Firth of Forth ; vicinity of Port Erin, Isle of I^Ian. 



Hemarks. The structure of the antennules, together with that of the antennte, the 

 mouth-organs, and fifth pair of thoracic feet, are characters by which Ectinosoma. g^xicile 

 may be distinguished from any other species described in this memoir. 



Ectinosoma cubticorne, Boeck (1864). (PL 36. figs. 22, 30, 34; PI. 37. figs. 10, 24, 

 41, 48 ; PL 38. figs. 8, 20, 35, 44.) 



1864. Ectinosoma curticorne, Boeck (i). 



1885. Ectinosoma curticorne, Poppe (g), p. 194, Taf. 6. figs. 1-12. 



1890 ? Bradya Edwardsi, Eichard (lo), p. 214, witli 10 figures in the text. 



1893? Ectinosoma Edtvardsi, Schmeil (n), p. 92, Taf. viii. figs. 1-21. 



1893. Ectinosoma ctirHcorne, I. C. Thompson (i6), p. 192, pi. xviii. fig. 8e. 



Description. Length '7 mm. (-^g of an inch). Somewhat like Ectinosoma Sarsi in 

 general appearance ; rostriun short and stout. 



Antennules very short and robust, 6-jointed; a somewhat roundish and dark-coloured 

 blotch occurs on tlie second joint of the antennules, as shown in the figure (PL 36. 

 fig. 34). The proportional lengths of the joints are nearly as shown in the formula: — 



No. of the joints : 1 . 2 . 3 . 4 . .5 . 6 _ 



Proportional lengths : 9 2 5 3 4 5 



AntennfB nearly as in Ectinosoma Sarsi, but the secondary branches are shorter than 

 the primary ones (PL 37. fig. 10). The biting part of the mandibles is broad and armed 

 interiorly with several small teeth, but the outer teeth are large ; the branches of the 

 mandibular palp are not so wide apart as in Ectinosoma Sarsi (PL 37. fig. 24). 



Anterior foot-jaws somewhat like those of Ectinosoma Sarsi, but very much smaller 

 (PL 37. fig. 41). 



Posterior foot-jaws short, moderately stout ; two plumose setse springing from the end 

 of the basal joint, while the terminal joint, which is very small, bears two lateral 

 plumose and spine-like sette and a plain and slender terminal hair (PL 37. fig. 48). 



The first foiu' pairs of swimming-feet are somewhat like those of Ectinosoma Sarsi, but 

 smaller ; the outer and inner branches of the foiu-th pair are also of nearly equal length, 

 and the lower marginal seta of the third pair is considerably longer than the others 

 (PL 38. figs. 8 and 20). The inner produced portion of the fifth pair extends to about 

 the middle of the secondary joint ; the terminal spines of both basal and secondary 

 joints are long and moderately stovxt, and l)oth joints (but especially the basal joint) 



