506 Mr. R. I. Pocock on the Morphology 



axis transverse and its posterior border straight or nearly so. 

 Jutting inwards on cacli side from the proximal end of the 

 coxa of the second leg is a movable maxillary sclerite, which 

 underlies and supports the labium, and the proximal end of 

 the coxa of the fourth leg projects forwards on the admedian 

 side of that of the preceding coxa, partially excluding it from 

 approaching the middle line of the sternal area. (PI. IX. 

 t^g. 1 A.) _ 



Jn the structure of its two sternal plates Ischyropsalis 

 resembles tlie Phalangiida?, as also in the forward prolonga- 

 tion of the proximal end of the coxa of the last leg. The 

 chief difference between the two, so far as the structures in 

 question are concerned, lies in the fact that the maxillary 

 })rocess of the coxa of the second leg is shorter and directed 

 vertically downwards *. (PI. IX. tig. 1 B.) 



In ^emasUma, DicranoJasma, TroyuIuSj and MefopocteOj 

 on the contrary, the labium is small, cordate or piriform, or 

 almost suppressed, and is lodged between the maxillary 

 processes of the legs of tiie first pair; its posterior border is 

 continuous w ith and flexibly fixed to the anterior end of the 

 sternum, and the sternum itself lies longitudinally, immovably 

 wedged between the coxEe, narrowed in front between those of 

 the first j)air ot legs and expanding posteriorly into a trian- 

 gular plate or a right and left branch, forming a X'^^'^P^d 

 sclerite. Moreover, there is no maxillary process on the coxa 

 of the second pair of legs, and the coxa of the fourth leg 

 does not send forward a jirocess on the proximal side of that 

 of the third leg. (PI. IX. figs. 2, 3 A, and PI. X. fig. 3 B.) 



I have been able to examine the sternum only in the 

 genera mentioned above. No doubt, however, a similar 

 arrangement will be found in the other genera of Trogulidte f- 



There is, then, a radical difference between the sternal 

 sclerites of the Phalangiida^ and Ischyropsalidse on the one 

 hand, and of the Nemastomidge and '^rrogulidae on the other, 



* As characters serving to distinguish Ischyropsalis from the Phalan- 

 giidse the fixity and smallness of the maxillary lobe of the second pair of 

 legs and the immobility of the coxaj of the legs have often been urged. 

 But neither the maxillary process nor the coxfe are fixed; tliey are 

 movable, as may be easily demonstrated by holding a specimen of Ischp-o- 

 jjsalis under the microscope and manipulating the parts in question with 

 a needle. They are not so movable as in the I'halangiidse certainly, but 

 equall}' certainly the coxiB are not fixed, as are those of Gonyleptes or 

 Trogulus, nor is the maxillary process fixed in the sense that the ocular 

 tubercle is fixed. 



t In his diagnosis of Amopamn Simon, in 1879, says "piece lahiale 

 plane et large " ; yet Sorensen, in ] 884, enumerates amongst the characters 

 distinctive of the Nemastomoidae and Troguloidfe, including Amopaum, 

 " labium sternale miiiutum.''^ I am unable to reconcile theee statements. 



