39 84 Proceedings of the Royal Irish Academy. 



margin of the second coxae. The thickened front margin of each of these 

 plates is very wide, and carries a single hair. The pedal shields are fused 

 inter se, enclosing the three last pairs of legs. The area genitalis is trapezoidal, 

 and lies opposite the third and fourth coxae. The anterior margin is rounded, 

 anterior part protected by a triangular shield, the pointed apex of which 

 reaches to about the middle of the genital area ; the side margins are 

 strengthened by narrow plates, hinder margin not chitinized. Ventro-anal plate 

 much smaller than in the male, long oval, narrowed in front, densely areolated 

 and punctured, armed with about four pairs of small bristles, and there are 

 two pairs of strong pectinated hairs on the hinder margin. On each side of 

 the ventro-anal shield is an oval inguinal shield. Peritreme (fig. 260 as in 

 male, tritosterum with a hatchet-shaped base, much larger than in the male, 

 filaments long and finely pectinated. 



Capitulum cup-shaped, maxillary plate with three pairs of long, widely 

 separated hairs. Epistome, palps, and mandibles closely resembling those of 

 the male. The legs are longer and less incrassate, their respective lengths 

 are 814 M , 748,,, 737/*, and 902,,. 



Nymph (fig. 26m). — An immature example, representing an early nyrnphal 

 stage, of the female was found at Westport in July. It measures 998/^ in 

 length, by 614ju in breadth. The general structure greatly resembles that of 

 the adult, except in the plate armature of the body. 



The dorsal surface is protected by five plates arranged as follows : — two 

 narrow marginal plates running from the chitinized frontal extremity to the 

 point where the peritreme turns inwards on the dorsum ; a large anterior 

 shield, which is somewhat cone-shaped, containing the first two pairs of 

 dorsal pits; at a little distance from this is a smaller semicircular plate, 

 emarginate in front, enclosing the third pair of dorsal pits, and immediately 

 behind this a small terminal plate similar to that of the adult. There are 

 indications that in the still younger nymph there may possibly be three pairs 

 of these central shields. Two sternal plates are present ; they seem, however, 

 to be fused on a chitinous base which reaches beyond them, and is deeply 

 excavated on its hinder margin, so that the nymph differs in this respect from 

 the adult female. There is a long ventro-anal shield, and on each side of this 

 two circular inguinal shields. The legs and ambulacra are like those of the 

 adult. 



Localities. — Found in some numbers under stones on the sea-shore at 

 Westport, County Mayo, in July ( $ , ? , and nymph). I have also found 

 both sexes in a similar habitat, between tide-marks on the south shore of 

 Howth, County Dublin, in the month of April. 



