44-0 MESSES. T. AND A. SCOTT— REVISION OF THE BRITISH COPEPODA 



twice the length of the preceding joint (PI. 36. fig. 33). The formula shows approximately 

 the proportional lengths of all the joints : — 



No. of the joint.s : 1.2.3.4.5.6.7 



Proportional lengths : 17 10 13 10 8 15 5 



Secondary hranches of the antennae 3-jointed and very slender, rather longer than 

 the second joint of the primary hranches ; the middle joint very small, but the 

 terminal joint is equal to about twice the length of the first (PL 37. fig. 8). Anterior 

 foot-jaws large and moderately stout ; terminal joint elongate-ovate, fully twice as long 

 as broad; terminal claws very long, the distal half fringed with cilia on the inner aspect; 

 terminal seta3 two, shorter than the claws and very slender (PI. 37. fig. 36). Posterior 

 foot-jaw^s elongated and very tenuated, the terminal joint nearly equal to half the length 

 of preceding one, while the middle ajoical seta is about tw'o and a half times the length 

 of the joint from which it springs (PI. 37. fig. 46). The inner branches of the first 

 pair of swimming-feet elongate, slender ; the outer branches, which are composed of 

 three nearly equal joints, are also slender, but scarcely reach to the end of the second 

 joint of the inner branches ; the fourth pair are stouter than the first, and the outer 

 branches extend somewhat beyond the end of the second joint of the inner branches 

 (PI. 38. figs. 1 and 24). 



In the fifth pair the middle seta of the secondary joint is extremely long and slender, 

 being nearly three times the length of those on either side ; the inner seta of the pro- 

 duced inner portion of the basal joint is nearly equal in length to the shorter setse of the 

 secondary joint ; the outer seta is slender and shorter than the inner ; the two outer 

 setse of the secondary joint and the longest seta of the produced inner part of the basal 

 joint are somewhat dilated or fusiform at the proximal end, — the longer of the two setae 

 on the produced part of the basal joint especially being very distinctly swollen near the 

 base ; a slender seta springs from near the middle of the hollow at the base of the 

 secondary joint, as shown in the figure (Pi. 38. fig. 40). 



Sabitat. Tirth of Porth, off St. MonanS. 



Memarks. This species, which somewhat resembles Ectinosoma gracile in general 

 appearance, differs quite distinctly from it by most of the characters described above, 

 but especially by the structure of the antennae, the very elongate and slender posterior 

 foot-jaws, and by the structure of the first and fifth pairs of thoracic feet. 



A List of some of the Works eeferred to in 9?his Memoir. 



1. BoECK, A. — Oversigt over de ved Norges Kyster iagttauge Copepoder (Soerskilt aftrykt af 



Videusk.-Selskab. Forhandl. Christiauia), 1864. 



2. BoECK, A. — Nye Slsegter og Arter af Saltvauds-Copepoder (ibidem), 1872. 



3. Brady, G. S. — A Monograph of the British Copepoda, 1878-80. 



4. Brady, G. S. — Report ou the Copepoda collected by H.M.S. ' Challenger/ 1883. 



5. Brady and Robertson. — Ann. & Mag. Nat. Hist. ser. 4, vol. xii. 1873. 



6. Canu, Eugene. — Les Copepodes du Boulonnais, 1892. 



7. Giesbrecht, W. — Pelagischen Copepoden des Golfes von Neapel, 1892. 



