126 Wallhui Limbs and Month in Ricinnlei 



margin, a small, excavated place (PI. VII., fig. 1 c), in which the stout distal extremity 

 of the fii'st trochanterial part of the palpus rests when drawn in towards the body. 



Karsch and Thorell have already demonstrated that all the legs have both patella 

 and tibia, and that whilst the first and second pairs have one trochanter, two such are 

 found in the third and fourth pairs of legs. It is only in Solifugfp that we find something 

 analogous to this last-mentioned structure, the first and second pairs of legs in Solifugse 

 having, as is well known, two trochanters, whilst the third and fourth have three. It is 

 true that in Opiliones a second trochanter is often found in the legs, but this is never 

 movable as against the femur. The direction of the movement between the coxa and the 

 first trochanter is essentially horizontal ; that between the first and the second trochanter 

 (on the 3rd and 4th pair of legs) rather slantingly horizontal, that between patella and 

 tibia purely horizontal ; but the movement between the second trochanter and the femur, 

 between the femur and patella, between tibia and metatarsus, and between the latter and 

 the tarsus, consists of simple flexiun and extension in the plane of the limb. 



The legs are entirely destitute of aculei ; not even spurs at the end of the metatarsus 

 or the tarsal joints are found. The second pair of legs is alwa3's a good deal longer than 

 the others ; the fourth pair is but little longer than the third ; the first pair is always 

 the shortest. 



The normal numbers of tarsal joints are, one on the first pair of legs, but four on the third 

 pair, and five on the second and fourth pairs of legs. It will, however, be shown below 

 that this does not hold good for all stages of development. In treating of the external sexual 

 differences we shall describe the peculiar development of the metatarsus and tarsus of the 

 third pair in the males. In the second pair of legs, the first three joints are shorter than 

 the fourth and the fifth, and their relative lengths afford a generic character; in the third 

 pair of legs (in females), the first three joints are very short and much shorter than the 

 terminal joint ; the same is the case with the first four joints of the fourth pair of legs. 

 Both in Gryptostemma and in Cryptocellus all the legs carry two claws, which are quite 

 simple, without teeth ; pseudonychium and scopula are altogether wanting. The end of the 

 foot on which the claws are jDlaced is deeply excavated, and the margin of the excavation 

 is on all the legs emarginate underneath ; the latter is also the case on the upper side on 

 the last two pairs of legs, particularly in Cryptocellus. The result of this arrangement is 

 that the claws are very " retractile " ; when drawn in they are less easily noticed on the 

 first two pair of legs than on the others. 



6. The Mouth. 



(PI. VII., figs. 1 A— 1 /(.) 



The mouth is formed exclusively by the mandibles and the labrum, the arrangement 

 resembling that in Uropygi. 



As shown in PI. VII., figs. 1 k and 1 on, the projecting part of the fused mandibles has the 

 shape of a trough, open above, which projects considerably more in advance of the labrum than 

 is the case in Oxopoei. Along the anterior margin of the mandibles and on theii' upper 



