200 DE. C. CHILTON ON THE SUBTEEEANEAN 



each is larger than the preceding. The coxa is deepei- than in the first four pair of legs 

 and is triangular, fitting into a triangular euiargination in the inferior margin of the 

 segment ; in the fifth segment this is at the posterior end, but in the sixth and seventh 

 it approaches nearer the centre, though still in the posterior half of the margin. The 

 basos is only slightly expanded, being oblong, about three times as long as broad, both 

 margins somewhat scantily supplied with setse. The ischium is very long, being consider- 

 ably longer than the basos, narrow oblong ; front margin straight, with five or six setae ; 

 posterior margin a little convex, with a few spiniform sette. The meros not half so long as 

 the ischium; postero-distal angle a little produced; both margins with spiniform setae, those 

 at the extremity being very strong. The carpus and propodos similar, the carpus usually 

 longer than the propodos; both oblong, and both margins supplied with spiniform setae 

 arranged in tufts, those on the anterior margin being larger than those on the posterior. 

 The dactylos as in the preceding legs, but longer and more slender. 



The above description applies to the fifth, sixth, and seventh pairs of legs, but it is to 

 be remembered that tiie spines as described above are larger and more numerous in the 

 sixth than in the fifth, and in the seventh than in the sixth. 



The pleopoda appear to be similar to those of P. ussimilis, but are rather more 

 slender ; the fifth pleopoda are very short and small. 



The uropoda (fig. 12) differ from those of P. assimilis only in being longer and more 

 slender, and in having the seta' on the inferior margin of the peduncle smaller and not 

 arranged in distinct tufts, but evenly distributed along the whole margin. 



In one of the females examined, brood-plates were beginning to appear at the bases of 

 the appendages of the perseon; one of these is shown in the drawing of the second pair 

 of legs (fig. 9) . 



Comparison of the three known Species of Phreatoicus. 



When I first received the specimens of the Phreatoicus from Winchester along with 

 the other species which were known from Eyreton (i. e. Calliop'ms subterraneus, Gam- 

 marusfragilis, and Cruregens fontanus), I naturally thought that they would belong to 

 the Eyreton species Phreatoicus typicus ; and thougli at the time I noticed that there 

 were a few variations, I thought that these might jirove to be due to differences of age 

 or sex. I was therefore somewhat surprised to find on a close examination that this 

 was not the case, but that the differences were quite sufficient to warrant the creation of 

 another species, viz. P. assimilis. Besides being found at Eyreton Phreatoicus typicus 

 is also known from Ashburton, only about 30 miles from Winchester, where Phreatoicus 

 assimilis is found ; and the existence of two subterranean species of the same genus being 

 so near each other is a fact of considerable importance, and it would be interesting to 

 know whether the species have differentiated since adopting a subterranean life, or 

 whether they have descended from two difierent surface species. It is therefore desirable 

 that the differences between them should be clearly set forth, and that they should be 

 compared not only with each other but also with the species Phreatoicus aiistralis [26], 

 found on the top of the Mt. Kosciusko plateau in Australia, and at a height of nearly 

 6000 feet above the sea. 



