39 122 Proceedings of the Royal Irish Academy. 



Halacarus (H.) ctenopus Gosse. 



Beeorded as occurring on weeds between tide-marks at " Westport and 

 Birterbury Bays " and at the " Isles of Aran (Galway Bay)." (Brady 19.) 



Distribution. —Littoral region of north-western Europe down to 64 metres 

 (44), and as far west as the Bermudas (45). 



Halacarus (H.) Basteri (Johnst.). 



H. spinifer Lohmann 40. 



Clare Island, nymph amongst weed on the coast in August (Irish Fisheries 

 Station W. 281) ; Blacksod Bay, female, with eggs, in March, and nymphs in 

 September. Has also been found at Ardfry on the Galway coast in May 

 (nymph), and on our eastern coast at Howth and Sandycove. 



Distribution.— A widespread species, occurring in the Baltic, North Sea, 

 English Channel, and the Atlantic, with a variety (qfflnis, Trouess.) in 

 the Mediterranean. 



Halacarus (H.) Southerni sp. nov. (PI. VIII, figs. 38a, b). 



This species belongs to the balticus group of Halacarus, and in some 

 respects resembles //. floriclearum Lohmann. It differs from the allied species 

 in the small size, in the form of the body, the armature of the first pair of 

 legs, &c. The inner spur of the third palp segment is very small. 



Female (fig. 38a). — Length about 385//, breadth 240/i. Hyaline, with the 

 eyes and a median spot, black. Form very broad, sub-ovate, fore-body 

 produced in a broadly rounded extremity covering most of the capitulum. 

 Side margins indented only at the origin of the third pair of legs, with one 

 shoulder bristle. Dorsal plates rather weakly chitinized and finely punctured. 

 Frontal plate rounded posteriorly ; eye-plate oblong and bluntly pointed ; 

 hinder dorsal plate long and tongue-shaped ; its front margin is truncated, 

 and lies quite close to the frontal shield. 



Capitulum (length, including rostrum, 165//, breadth 75/*), with the hinder 

 margin somewhat truncated, and the sides are rounded ; rostrum of a rather 

 broad, triangular form, its apex does not reach the end of the second palp 

 segment. The third palp segment is armed with a minute inner spur. 



Legs moderately long and robust, first and second pairs of very similar 

 structure. The length of the first leg (fig. 38&) is about 350/1, dorsal surface 

 of third segment strongly humped before middle, with a pair of distal hairs ; 

 fourth segment with one ventral and three dorsal hairs, and near the former 

 is a strong spine ; fifth segment with two long hairs in addition to the 



