Clare Island Survey — Acarinida. 39 35 



pectinated. Fourth segment very broad at the base, strongly narrowed towards 

 the apex. The sword-bristle reaches well beyond the end of the segment. 



The female (PI. II L, fig. 26 d) of this species may be easily identified by 

 its large size and peculiar shape. An example from Dartrey Lough measures 

 1-53 mm. in length, by 1'20 mm. in breadth. The body is very strongly 

 narrowed in the anterior half, and the front margin is evenly rounded, 

 posterior corners very slightly raised in a rounded prominence. The eprmera 

 are very much smaller than in the male. The genital area lies close to the 

 fourth epimera, and is widely removed from the end margin of the body. 

 The front margin of the tongue-shaped plates springs from the middle of the 

 chitinous rim of the genital orifice. Legs shorter than in the male. 



Localities. — Upper Lough Erne, September, 1899 ; Dartrey Lough, County 

 Monaghan, October, 1899 ; lake in the north-east of Achill Island, County 

 Mayo, June, 1909. 



Arrhenurus forpicatus ISTeuman, var. perforatus George. (Plate III., fig. 28-29.) 

 Lakes near Westport, June ; Lough Baun near Louisburgh, amongst a 

 dense growth of Chara, July. 



The specimens found in this district are all to be referred to the variety 

 perforatus George. It may be readily separated from the typical form by the 

 structure of the petiolus. In the males of forpicatus the ends of the dorsal 

 furrow are continued obliquely on the appendage, enclosing the highly 

 chitinized petiolus. This is oblong and swollen at the centre ; and as it is 

 rather complex, its structure may be best shown by a figure (PI. III., fig. 29). 

 In the perforatus form, on the contrary, the ends of the dorsal groove run 

 parallel for a short distance on the appendage, and are evenly rounded at the 

 apex. The petiolus (PL III., fig. 28) is much simpler, being a small prominence 

 placed close to the concavity of the hinder margin of the appendage. As 

 Piersig has pointed out, there are some differences in the shape of the 

 appendage between the two forms, but the structure of the petiolus is quite 

 sufficient to distinguish them. In the female of the perforatus form the 

 genital plates are somewhat narrower and more pointed at the free extremities 

 than are those of the typical form. 



The variety perforatus would seem to be the prevalent form in Ireland ; all 

 of my Dublin specimens are to be referred here. The only Irish examples of 

 forpicatus that I have hitherto met with are from Loosecaunagh Lough near 

 Killarney. 



Arrhenurus sculptus Halbt. (Plate III., fig. 25 a-c.) 



Bog pools on Cartron Mountain, near Letterfrack, County Galwav. 

 March, 1904. 



E 2 



