The 3Ioiith In Rkhmlei 127 



concave surface there is a close covering of long, delicate blood-hairs', which are slightly plumose 

 all round. Referring to our fig. 1 m, we interpret the whole middle portion as the labrum 

 divided into two parts, which we describe as purs apicalls (e) and pars hasalis (/). Across 

 the entire middle of fig. 1 m a straight line (/) will be noticed, from which the soft membranous 

 skin which e.\tends to the antennaj and the posterior extremity of the cucuUus apparently 

 starts. In front of this transverse line the projecting portion of the mandibles is seen as 

 well as the whole of the pars apicalis (e) of the labrum and a short portion of the pars basalis, 

 which portion is considerably broader than long. It will be noticed also that the dorsal 

 surface of each of the mandibles is continued far behind the transverse line, nearly parallel 

 to each other, their posterior extremities being rounded, and finally that pars basalis labri 

 is continued behind the transverse line rather farther back than the mandibles in the shape 

 of a somewhat convex plate, which is likewise rounded at its posterior extremity. Pars apicalis 

 of the labrum fulfils the ordinary functions of a labrum, its anterior and lateral margins 

 being free and limiting the oral orifice; its integuments are everywhere thin, and its upper 

 surface, at any rate, is covered with numerous rather long hairs ; we have not been able 

 to obtain certain knowledge of its lower sui'face, but so much is certain, that this part does 

 not contain any muscles. The dorsal surface of pars basalis is, on the contrary, firmly chitinised, 

 naked, and, through the whole of its length, fused with the dorsal part of the mandibles. 

 Besides, the pars basalis contains a well-developed set of muscles which we shall presently 

 describe. In the cavity of the mouth, that is the space between the mandibles and the 

 pars apicalis of the labrum, the whole of the bottom and the side walls, consequently the 

 whole of the surface of the mandibles, is covered with hairs which are directed forwards 

 and towards the middle of the cavity. These are very different from those that cover the 

 upper surface of the mandibles, being short, and placed so closely together in regular lines 

 that the surface where they grow assumes the same appearance as the line-ornamentation 

 on the back of many watches. As shown in fig. 1 k and particularly in fig. 1 ^ a transverse 

 chitinous crest originates from the lower side of the plate which is formed by the mandibles 

 and the pars basalis of the labrum ; this crest (c) has the back concave, whilst its ventral 

 margin is bent a little forward, and it is perforated by the oesophagus {d). We have noticed 

 five sets of muscles in this region, viz. 1. and 2., the muscles (PI. VII., figs. 1 v and 1 k, /«' and iii-) 

 which move the first trochanterial part of the palpi, and which arise partly from the dorsal 

 side of the mandibles, partly from the anterior face of the chitinous crest (c) just mentioned, 

 and the dorsal side of the hindmost part of the mandibles, 3. {m^, fig. 1 k) the pumping muscle 

 of the oesophagus or pharynx, which arises from the pars basalis of the labrum behind the 

 transversal crest, 4., a muscle (/«■" in fig. 1 n) attached to the base of the pars apicalis of the 

 labrum, which probably serves to move the latter; finally 5., a muscle {iii^, fig. 1 n.) situated 

 in the middle line, of which the function is doubtful to us. 



Any doubt as to the correctness of our view, that the whole middle portion of the 

 piece figured PL VII., fig. 1 m is to be looked upon as formed by the labrum, will be removed 

 by comparing the stmcture we have described in Cryptostemma with that found in Uropygi ; 

 the similarity as regards the labi'um and the dorsal portion of the mandibles being very 

 striking. Both in Oxopoei and in Tartarides the labrum consists of a pars apicalis, characterised 



' On tbis term see p. 124, at the top. This is at auy auy chitiuous wall as background — but we do not know of 

 rate the character of all the hairs which we have had au what- kind the hairs are on the upper surface of the labrum. 

 opportunity of examining against the light — without having 



