102 BRITISH PARASITIC COPEPODA. 



two-jointed, but those of the third and fourth pairs 

 uniarticulate, tolerably large, and lamelliform. Length 

 about 20 mm. 



Male. — The male does not differ greatly from the 

 female, but it is only about half or three-quarters the 

 size, and the dorsal plates of the thorax and genital 

 segment are proportionately smaller ; the dorsal plates 

 of the genital segment have also their inner margins 

 apparently coalescent except at the posterior end, 

 where they are separated by a moderately deep sinus; 

 they scarcely extend so far back as in the female, so 

 that the caudal rami are exposed. 



The antennas and the second maxillipeds are also 

 stronger and form more powerful grasping organs than 

 those of the female ; the rami of the third pair of 

 thoracic legs are not foliaceous, but, like the first and 

 second, are biarticulate ; they differ however in the 

 inner ramus being small and somewhat rudimentary. 

 The fourth pair are similar to the fourth pair in the 

 female. Length from 10 to 15 mm. 



In both sexes the colour is dull yellow. 



Habitat. — Parasitic on the short sun-fish, Ortha- 

 goriscus mola. " Specimens taken off Plymouth were 

 given to A. M. Norman a great many vears ago by the 

 late Mr. C. Spence Bate."* Moray Firth (T. Edward). 

 Firth of Forth, October 1890 (A. Scott). Dr. Baird 

 records this parasite on the authority of W. Yarrell, 

 but does not mention the locality. On a short sun-fish 

 captured off Berry Head, 1898 (Major E. V. Elwes, 

 Babbacombe) . 



Distribution. — European Seas. South Africa 

 (T. B. B. Stebbing). New Zealand (67. M. Thomson). 

 The Atlantic and Pacific coasts of North America 

 (C. B. Wilson). 



* ' The Crustacea of Devon and Cornwall,' 1906, p. 211. 



