39 6 Proceedings of the Royal Irish Academy. 



third segment the prominence is only slightly developed, with about eighteen 

 spines. The fourth segment shows a pronounced hump near the base, lower 

 half of the inner surface with about twenty long spines, not including a row 

 of strongly pectinated ones placed distally ; the lower outer margin has about 

 seven long bristles. Apex of the fifth segment furnished with eight or nine 

 short, stout, and bluntly pointed teeth. 



Many of the Mayo specimens are fully grown, the males measuring about 

 3 mm., while the females often reach 5 mm. in length. A figure of the male 

 genital area, which has not apparently been previously figured or described, is 

 given (PI. I., fig. 26), and it will be seen that it is very different from that of 

 E. infwndibulif&ra figured by Koenike (12, etc.). 



Eylais infundibulifera Koenike. (Plate I., fig. 3.) 



This species was found in the neighbouring parts of Galway. A figure of 

 the eye-plate, which is large and variable in shape, is given on Plate I., fig. 3. 



Eylais relicta nov. sp. (Plate I., fig. 5 a-/.) 



During a visit to Connemera in September, 1905, an Eylais occurred in 

 Glendalough Lake which I was unable to identify at the time. Another 

 specimen, not quite fully developed, of the same species occurred in Castlebar 

 Lough (June) during the Clare Island Survey, and a third still smaller specimen 

 found in a tarn on Cromaglaun Mountain, Killarney, is also to be referred 

 here. The species may be compared with infundibulifera, and appears to be 

 un described. 



The eye-plate (PI. I., fig. 5) is highly chitinized, and rather smaller. The 

 measurements are as follows : — 



Breadth across anterior lenses, "407 mm. 



Breadth of bridge between the lenses, - 110 mm. 

 Breadth between the hair-pores, '077 mm. 



Length of eye-plate, '142 mm. 



The front margin of the eye-plate is produced in a broad prominence which 

 is truncated at the apex, and shows, in the type-specimen (Glendalough Lake), 

 a cone-shaped subcutaneous part resembling Thon's figure of E. meridionalis. 

 The posterior concavity may apparently be either acute or somewhat rounded 

 at the apex. The reticulated eye-plate is remarkably broad behind, and 

 distinctly narrowed in front on the inner side, much as in E. latipons Thon, 

 while the outer margin is only moderately sinuate. The anterior lenses are 

 comparatively small and stalked. The hair-pores are placed at some distance 

 from the eye-plates, and underlying them is a chitinous ring, which is more 

 strongly developed in the smaller specimens. 



