Clare Island Survey — Apterijgota. 32 5 



coxa of the eighth abdominal segment, by the ammlation of the gonapophyses, 

 and by the extreme shortness of the penis, which does not reach as far as 

 the sub-coxae of the ninth segment. It is of great interest to find that our 

 western Petrobius serves as a connecting link between the Continental and 

 eastern Irish species on the one hand — with which it agrees in its unannulated 

 gonapophyses — and the North American species (Pedetontus) on the other, 

 which it resembles in its simple eighth abdominal sub-coxae ; as regards the 

 length of penis, it seems quite intermediate. The general aspect of this 

 species is well enough delineated in Lubbock's coloured plate (1873, pi. liv). 

 His details of structure (I.e., pi. lxvi) do not emphasize points of importance 

 in differentiating between the two species now under discussion; but the 

 lengths of the gonapophyses and penis, and the slender elongate stylets in his 

 plate lxvi, fig. 7, seem clear evidence that he had the present species before him. 

 . For further details reference may be made to the figures accompanying 

 the present paper. It is only necessary to call attention to a few additional 

 points in connexion with the jaws. Those of the female are generally 

 larger and stronger than those of the male ; but reference has been made 

 above to the slight suggestion of apical teeth on the mandibles of the 

 latter sex, which in some cases show also a few conical teeth near the 

 molar area (fig. 3). The lacinia of the maxilla terminates in a somewhat 

 blunt tooth (fig. 5), from the inner face of which project two delicate 

 lamellae ; between these, a hairy process, like an elongate brush, may be 

 seen. The basal segment of the maxillary palp has two processes, a longish 

 acute dorsal and a small rounded ventral lobe ; these are far more prominent 

 in the female (fig. 5) than in the male (fig. 4). The labial palps are remark- 

 able — probably in all species of Petrobius — for the curious, broad, flattened 

 spines, with minute processes on the terminal segment (figs. 6-7). These 

 vary in shape among themselves, and show a number of fine longitudinal 

 striations. The labrum (see fig. 1) is beset with long bristles and a number 

 of short, stout spines at the tip. The maxillula has already been figured in 

 the Proceedings of the Academy (vol. xxiv, p. 324). The comparative 

 structure of the various species of Machilidae is worthy of careful study. 

 Superficially alike, the allied forms may be readily distinguished by definite 

 details of the jaws and abdominal appendages. 



COLLEMBOLA. 

 PODUEIDAE. 



Achorutes annatus (Nicolet). 

 A few specimens in moss (J. E". Halbert, August, 1911). 

 The species, though not common, is widespread in both Great Britain 



