Halbiokt — Th£ Acarina of the Seashore. 131 



Sub-Older OltlBATOIDEA. 



Family ORIBATIDAE. 



Oribata setosa G. L. Koch. 



Malahide, under more or less dry Hakes in the Orange Lichen zone ; also 



under refuse lying on the rocks in the same zone, April and May. A widely 



distributed species. 



Oribata quadricornuta Michael. 



Found by Mr. Southern in the Orange Lichen zone at Lough Hyne, 

 Co. Cork, November, 1916. At Mulranny it was also found under stones on 

 the seashore in September. 



Oribata quadrivertex sp. nov. (PI. XXII, fig. 15 a, b.) 

 A small, compactly formed species, standing nearest to the " pyriformis" 

 group. It is remarkable on account of the short, strongly clubbed pseudostig- 

 matic organs, the square vertex, and the peculiar form of the lamellae, which 

 in tire long, slender cusps bear some resemblance to those of Oribata gracilis. 

 Occurs in salt marshes. 



Length, about 450/x ; breadth, 2S0/i, and slightly larger. Colour, 

 yellowish brown; texture smooth and shining. Cephalothorax (fig. 15a) 

 rather short, about one quarter as long as the abdomen, and much narrower. 

 Rostrum bluntly pointed ; dorso-vertex quadrate, half hidden by the central 

 extension of the dorsum. The lamellae are narrow, uniform bands con- 

 nected by an equally broad translamella ; cusps rather long and slender, and 

 just broad enough at their extremities to carry the lamellar hairs ; these are 

 stout and curved strongly downwards over the rostrum. Interlamellar hairs 

 long, very stout, and minutely serrated ; they spring from a transverse bar 

 wbich bounds the posterior margin of tlie dorso-vertex. Pseudostigmatic 

 organs (fig. 15 b) close to the middle line of the body, short and strongly 

 clavate, slightly incurved, and their stems are mostly hidden under the 

 margin of the dorsum. The stigmata are cup-shaped, shallow, and their 

 margins are but little raised. First tectopedium a long curved blade. 



Abdomen oblong, shaped much as in 0. gracilis, though less strongly 

 narrowed in front, evenly rounded at end margin ; pteromorphae weakly 

 developed. Front margin produced at centre in a small rounded prominence, 

 dorsum with about eight pairs of minute hairs, two pairs on enil maigin 

 upturned and stronger than the others ; there is a circular pore near the sides 

 of the dorsum. Genital and anal plates large, of almost equal size, each 

 enclosed by broad chitinous margins. Epimera without the distinct inner 



