46 BRITISH COPEPODA. 



abdomen in the female, still less in the male (figs. 1, 9). 

 Length about ^th of an inch (1/3 mm.). Colour 

 yellowish or reddish yellow, quite transparent. 



P. elongatus is a very common species, being dis- 

 tributed all round the British Islands between tide 

 marks and in the open sea. It is often met with in 

 considerable numbers. M. Boeck points out that in 

 some specimens, which he supposes to be females, 

 there are traces of a fifth foot in a rudimentary stage. 

 I at one time also held this belief, but am indebted to 

 Dr. Claus for suggesting to me that these specimens 

 are in reality immature males, and that along with the 

 imperfectly formed feet there are usually also other 

 signs of immaturity in the animal. The female must, 

 therefore, be considered to be constantly destitute of a 

 fifth pair of feet. 



2. PSEUDOCALANUS ARMATUS, BoecJc, PL IV, figS. 1 11. 



Pseudocalanus armatuB, Boeck. Nye Slaegter og Arter af Salt- 

 vands-Copepoder, p. 6 (1872). 



Body elongated (fig. 1) ; head quite distinct from 

 thorax; fourth and fifth thoracic segments coalescent, 

 and produced at the dorsal angle into a strong back- 

 ward-projecting spine; ventral angle rounded off. 

 Anterior antennie in the female stout (fig. 2), 

 as long as the cephalothorax ; 1st and 2nd joints 

 large, and longer than the next following ten joints, 

 which are short and broad; the 13th joint is about 



