134 BRITISH C0PEP0DA. 



does not show correctly the relative lengths of the 

 joints in the adult). The first pair of feet (fig. 8) have 

 both branches broad, 3-jointed, and of nearly equal 

 length, all the joints short and broad, the terminal 

 ones broadly rounded or subtruncate at the apex ; 

 marginal setse long, stout, and densely plumose ; 

 spines of the external branch long and stout. The 

 second, third, and fourth pairs (fig. 9) are longer than 

 the first, the spines of the external branch are smaller, 

 the setas also much smaller and destitute of plumes. 

 The fifth pair consist each of a single small bisetose 

 lamina. The caudal segments are about as long as 

 the preceding four abdominal rings, slender, curvate, 

 and jointed near the middle, the apices bearing three 

 minute hairs (figs. 11, 12).* Length y^-th of an inch 

 (2-1 mm.). 



Many immature specimens of this species were 

 found in Ascidians dredged by Mr. Robertson, the 

 Rev. A. M. Norman, and myself, off* the coasts of 

 Durham and Yorkshire, and also by Mr. Norman at 

 Oban and Shetland. Except a few kindly sent to me 

 by M. Thorell, I have seen no adult of D. pulex. On 

 this account, probably, my drawings do not in all 

 respects agree with those of M. Thorell. The British 

 species of the genus, and, indeed, all the Ascidian 

 parasites of Britain require much closer and more 



* The figures of anterior antennse and caudal segments given in 

 PI. XXXI, figs. 1 and 2, represent either an unnamed species or a 

 variety of D. pulex ; at present I prefer to adopt the latter supposition, 

 as the general characters of the specimens coincide with those of D. 

 pulex. The specimens were found by Mr. Norman in Ascidians from 

 Roundstone Bay, Ireland. 



