39 82 Proceedings of the Royal Irish Academy. 



Thinozercon n. gen. 



The dorsum is protected by three dorsal plates (more or less fused in the 

 male). There are two, paired, sternal plates in the female (fused in male), a 

 fused ventro-anal shield and two inguinal plates. Pedal plates well developed, 

 uniting behind the fourth acetabula. Peritreme placed on the dorsal margin of 

 the body. Epistome unispinous, with strong lateral teeth. Legs incrassate. 

 ambulacra present on all pairs. Male genital foramen in the centre of the 

 sternal shield, the latter is entire, not joined to the ventro-anal plate, which 

 is large, and includes the fused inguinal shields. Second legs of male without 

 special armature. Type species Thinozercon Michaeli sp. nov. 



Thinozercon Michaeli sp. nov. (PI. VII, fig. 26a-m.) 



Male (fig. 26a). — Length 1075^, breadth 568/u ; colour, golden-brown ; 



shape, long oval, sinuate in front of the shoulders ; the latter are low and 



rounded, anterior extremity produced in a small prominence, carrying two 



broad serrated bristles. Dorsal surface protected by one fused shield, in 



which can be traced the outlines of three plates which are separate in the 



female; moderately convex, with three pairs of circular pits. The dorsal 



plate folds over and protects the anterior ventral margin. Epidermis finely 



punctured, and closely areolated. There is a double row of short spines in 



the middle line, and a row of sub-marginal spines, end of the body set with 



adpressed bristles, some are feathered. Sternal plate large, fused with the 



first and second endopodial plates, front margin wide, undulate ; the side 



margins send sharp processes between the last three pairs of legs ; the end of 



the sternum tapers to an obtuse extremity between the fourth acetabula. 



There are five pairs of very short hairs on the sternum. The pedal plates 



form a continuous line on the outer side of the leg bases, curving inwards 



behind the last acetabula, where they form a pair of platedike expansions 



fused with the last pair of inner pedal plates. A large ventro-anal shield 



occupies the hinder part of the body, leaving a very narrow margin between 



it and the dorsal shield, surface punctured and reticulated. The anal aperture 



is on a raised cribrum. The peritreme is of remarkable structure, originating 



on the front of the body, it follows the upper margin to a point opposite 



the interval between the third and fourth legs, it then curves round on itself, 



so that the stigmal extremity resembles an inverted interrogation mark. Base 



of tritosternum wide, stem stout, dividing to form a pair of long pectinated 



filaments. On the inner side of these, at the base, there is a short pointed 



process. The genital foramen is a small circular aperture between the third 



