132 MR. G. S. BRADY ON THE CRUSTACEAN FAUNA OF THE 



foot-jaw having its margins nearly equally arched, lower margin 

 bearing in the middle a long seta, with several minute ones in 

 front of it ; claw long and slender. First pair of feet strong, 

 outer margins of the two branches densely setose and spinous ; 

 outer branch very much shorter than the inner ; the long branch 

 bearing on its inner margin a single long plumose seta, which 

 never reaches much beyond the base of the terminal spines. 

 Fifth pair of feet somewhat larger, and less angular in the fe- 

 male than the male, bearing several long apical setae. Abdomen 

 broad, its last segment short ; caudal segments also very short, 

 inner tail-seta3 fully two-thirds the length of the body, outer 

 seta about half their length. Length, ^-g-th of an inch. 



Hab. — ^In rock pools at Eoker, county of Durl^am ; and the 

 Great Isle of Aran, G-alway Bay. Also in pools of brackish 

 water at Seaton Sluice, Northumberland. 



This species is less common than that which I at one time 

 supposed to be referable to D. tisboides, and which I published 

 under that name in the "Intellectual Observer" [loc. cit.). The 

 form of D. tisboides found in brackish water differs remarkably 

 from the marine form in the strength of the spinous and plumose 

 armature of the limbs. I do not know that this variation is pro- 

 duced by difference of habitat, my observation of the species not 

 having been extensive enough to assure me that a similar variety 

 may not be found in truly marine situations. The following re- 

 marks of Dr. Claus on a similar variation in one of a nearly allied 

 genus, will, however, be read with interest: — "The stronger, 

 and, on the average, the larger form of Harpacticus niccaensis has 

 a heavy, strong body, ill-bred apparently, inactive, and wanting 

 in mobility ; the antennae clumsy, with their third and fourth 

 joints short and thick, the second joint very long ; the second 

 foot-jaw ends in a strong, massive, clasping hand ; the first pair 

 of feet are armed with doubly curved claws ; the feet, especially 

 the last pair, are strong and clumsy, all the setae showing a ten- 

 dency to become plumose. The smaller and slenderer breed has 

 larger antennae , the third and fourth joints of which are much 

 elongated ; the prehensile apparatus of the foot-jaws and first 

 pair of feet more slender ; and there is also a much glimmer, 



