1 38 BRITISH COPEPODA. 



the spines of the first feet* (fig. 12). Whether these 

 distinctions will be fonnd on further research to hold 

 constantly good, one may perhaps doubt, but for the 

 present there seems no sufficient reason for withholding 

 from this form a specific name. But the inconstancy 

 of characters amongst the Notodelphyidas is extremely 

 bewildering, and until much more attention has been 

 paid to them it is impossible to define with accuracy 

 the limits of species. In this particular instance 

 the difficulty is the greater owing to M. Thorell's 

 imperfect account of his Dovopygus psyllus, of which 

 he had found only two specimens, a number which 

 is often insufficient for the purpose of complete 

 description. 



Doropygas Normani occurred in some abundance in 

 a collection of parasites found in the cavities of 

 Ascidians which were taken between tide-marks at 

 Roundstone, Ireland, by the Rev. Alfred Merle 

 Norman, whose name I am glad to have the oppor- 

 tunity of associating with the species. 



4. DOROPYGUS PORCICACJDA, 110V. S$). PI. XXVII, figs. 



1—9 ; and PL XXXIII, 14—16. 



Adult 



female. — Basal joint of the anterior antenna 



* The substitution of setse for spines on the margins of the external 

 branches of the swimming feet is an important feature, if constant, 

 but in some examples one or more of the set® were wanting, and there 

 seemed to be small spines closely adpressed to the limb ; I could not, 

 however, satisfy myself whether or no these might be the scars or 

 broken extremities of lost setse. 



