MR. LUBBOCK ON THE THYSANURA. 435 



smaller and more slender than the first (PI. XLV. fig. 11). At its free end it is pro- 

 duced into two processes and a small spine. The shorter process reaches about as far as 

 the free end of the other organ, and is like a spine in form, though apparently not so stiff; 

 the second process is somewhat longer, and whip-like. 



The anterior legs are the shortest, and the posterior the longest, the middle pair being 

 intermediate in size as well as in position. The relative proportions of the segments, as 

 well as the structure of the foot, are the same in all three pairs. The tarsus is very short ; 

 the tibia is much the longest segment. The coxa, trochanter, and femur diminish in 

 diameter, and increase in length. At the attachment of the leg are one or two deep folds, 

 which, however, are not, I think, to be considered as indicating true segments ; and we 

 may therefore consider the segments as being five in number. The legs are regularly, 

 but not very densely, clothed with hairs. 



Anterior abdominal appendage. — This organ, which is attached to the sternum of the 

 anterior abdominal segment, did not escape the attention of M. Nicolet, who, however, 

 describes it as " une petite piece blanche, saillante, multiarticulee," while in the present 

 species, as well as in the other two observed by me, it has at most two segments, and is of 

 a dark colour. In Smyntlmriis Buskii it consists of a large quadrate basal piece, which 

 is somewhat widest at its proximal end, and bears at the side two small appendages, of 

 which the one nearest to the apex is bilobed. The terminal segment is swollen at the 

 base, and rounded at the extremity, where are four small setse. 



M. Nicolet considers that this organ serves to retain the spring in its place. It is 

 generally turned backwards, and lies in such a position as to lap over the basal part of 

 the spring, between the two lameUse, which perhaps are in part covered by the small 

 lateral appendages ; and, by the pressure which it thus affords to the tension of the 

 muscles, he supposes that it adds force to the spring. However this may be, it seems to 

 me to be homologous with the anterior abdominal appendage of Lepismidse, the basal 

 portion being, however, very much developed, and the lamella3 only represented by the 

 small lobes at the apex. 



The spring is attached, according to Nicolet, to the penultimate abdominal segment ; 

 this, however, is apparently an oversight, since in pi. 3. f. 6, he figures it on the under- 

 side of the great antepenultimate segment. 



Excepting in one case (^S*. ornatus), M, Nicolet does not allude to the form of this organ 

 as affording any specific characters ; but, as wiU be seen by comparing our PL XLV. 

 figs. 12, 13, and PI. XLVI. fig. 24, the structure is by no means the same in all species. 



The organ consists, as usual in the Smynthuridse, of a basal portion and a pair of two- 

 jointed appendages. 



If we take a specimen in which the basal portion is about -01" in length, the 

 breadth will be about -014"; the first segment of the appendage will be -0225" in 

 length, and gradually taper from a width of -0065" at the base to -003" at the apex. 

 It bears many scattered hairs, most of which are simple and about -005" in length. On 

 the inner margin, however, are three hairs of very different structure. They have a 

 length of -014", and gradually taper from the base to the apex, where, however, they 

 suddenly swell up into a delicate oval structure, something like the button at the end of 



