MR. LUBBOCK ON THE THYSANURA. 437 



On the latter they are arranged in whorls, giving the organ an appearance of being jointed, 

 which, however, is not really the case. 



The mandibles much resemble those of S. JBnskii ; I found, however, in my specimens 

 six apical teeth on one mandible, and only four on the other. 



The maxillse also resemble those of the preceding species. The arrangement of the 

 teeth is, however, a little different ; and they appear to be rather more numerous ; or at 

 least the two e and/, fig. 6, have each a large secondary lobe at the base. 



The palpus is simple, short, -005" in length by -002" in breadth, and rounded at 

 the apex (PI. XLV. fig. 19) ; it bears one long and two or three short hairs, not at the 

 apex, but almost in the middle of its length, though rather nearer the free end. The 

 organ is membranous, and in most parts transparent. 



The upper lip is about -00416" in width, and is quadrate in outline, with the corners 

 rounded off. The free edge is roughened by minute teeth, which are largest towards the 

 centre. On each side there is also a row of larger teeth, parallel with the anterior mar- 

 gin, and with the teeth pointing inwards. The organ is also provided with scattered 

 hairs. 



The organ which I have suggested to be the representative of the second pair of maxillae 

 is represented in PL XLV. fig. 20. In my specimens it differed slightly from that of 

 P. Saunclersii in outline, as well as in the possession of two minute teeth. Whether 

 these differences are constant must be decided by the examination of other individuals. 



The under lip resembles that of P. Smmdersii (PL XLYI. fig. 30). 



The legs are longer in proportion, but at the same time thinner, than those of the pre- 

 ceding species. The proportions of the different legs are the same, the anterior being the 

 smallest, and the second pair intermediate in size between that and the third pair. In the 

 relative sizes of the different segments also this species agrees very closely with Smynthurus 

 Buskii — the coxa being short, and the three following segments increasing in size almost 

 in a geometrical ratio. The whole organ, except the tarsus, is clothed with scattered hairs, 

 which, however, are most numerous on the tibia. The tarsus itself is short and bare. 

 The appendages of the tarsus are manifestly (PL XLY. figs. 22, 23) arranged on the 

 same type as in S. Buskii, though the details so far differ as to offer good specific 

 characters. The outer spine {a) is not elliptic, but resembles in outline the blade of a 

 clasp knife, and has two strong teeth on the imder edge. The second inner appendage {b) 

 also presents weU-marked differences. The basal portion bears a small, cvirved spine, and 

 in the first foot (fig. 22) gradually contracts, while in those of the third pair- (fig. 23) there 

 is a sudden diminution immediately beyond the basal spine. The tip of the filament 

 (PL XLV. fig. 23 c) appeared to me to be slightly swollen. In this character it presents 

 much analogy with the so-called "tenent hairs" described by Mr. Tuffen West in the 

 twenty-third Volume of the ' Transactions of the Linnean Society ;' see, for example, 

 his figures of these hairs on the tarsus of Ocypus olens (PL XLII. fig. 24 i), or those 

 from Mylabris cichorice (PL XLII. fig. 29). In both those cases, however, the hairs are 

 very numerous, and their combined action is no doubt sufficiently efficacious ; but in this 

 case, where we have only a single hair on each foot, its action must be very slight. 



The spring in this species is rather longer and slenderer than that of the preceding. 



