Mandibular Palps and walkhaj Lhnhs in, Hicimdei 125 



any kind. The femonil part is always stout, though not ec^ually so in all species ; it is 

 always stouter in adult specimens than in young animals (compare PI. VIII., fig. 3 d with fig. 3 e). 

 In shape it is but slightly compressed or not at all, and a greater or smaller part of its 

 distal portion presents a longitudinal excavation of the ventral surface. The tibial part 

 of the palpus is more than half as long again as the femoral part, and at the same time 

 much less stout; it is cylindrical, but of somewhat different shape in different species; 

 it can be — and is in reality often found — bent inwards along and close to the ventral 

 surface of the femoral part. On its ventral surface, close to its distal extremity, it carries 

 a small process of which the dorsal margin, at least sometimes, is distinctly serrate, and 

 against that the tarsal part can be adduced, so that together they form a small chela. The 

 tarsal part is always very small, but at the same time always considerably larger than the 

 process on the tibial part; like the tibial part it is capable of movement only in the 

 2)lane of the limb, that is to say, of fiexion and extension. 



In so far as the palpus in Ricinulei terminates in a small chela it may be said to 

 present some similarity to the same appendage in Thelyphonoidae. But otherwise it is, as 

 we have already pointed out, very different from what appears in all other Arachnida, 

 chiefly on account of the remarkable torsion between the second trochanterial and the 

 femoral parts. By this means the animal is enabled to direct the end of the palpus both 

 forwards and backwards, as we have shown in PI. VII., fig. 1 b, where we have represented 

 one of the two palpi in each of the opposite positions. On account of the niovability 

 in the two first articulations the palpus is able to reach the mouth with its end, in either 

 of these positions. 



As regards the number of joints in the palpi, Ricinulei do not differ from other orders 

 of Arachnida except Acari'; the number being five in them all; and it would be quite 

 natural to suppose, as indeed has been done, that these five joints represent the same 

 sequence of homological equivalents in all cases. But this would be an error, as may perhaps 

 be proved in the clearest manner by comparing the palpus in Ricinulei with that in Aranese. 

 In both orders the basal joint of the palpus is trochanterial, and the la.st tarsal, but whilst 

 the second part in Ricinulei is trochanterial like the first, and the third is femoral, the 

 second joint in the palpus of Aranese is femoral, and the third a patellar part. 



3. The walking Limbs or Legs are in several respects rather peculiar. As we have men- 

 tioned already, the three first pairs of coxa; are immovably coalesced, whilst the fourth pair is 

 free and capable of a limited rolling movement forwards and backwards, a combination 

 which is unique amongst Arachnida-. In describing the mechanism of the coupling together 

 of the abdomen and the thorax we have pointed out the correlation between this arrange- 

 ment and the movability of the fourth pair of coxse. As in Uropygi the proximal extremity 

 of the first pair of coxse (PI. VII., fig. 1 c ; PL IX., fig. 3 b) commences at a point considerably 

 nearer the side of the thorax than the proximal extremities of the second, third, and 

 fourth pairs; but the fact that the coxse of each of. these pairs touch one another in 

 the middle, so as to render the sternum altogether invisible, constitutes a difference between 

 Ricinulei and Pedipalpi, though these latter, as is well known, differ amongst themselves 

 in this respect. On the under surface of the first pair of coxa; there is near the anterior 



' In Palpigradi (Kcenenia) this pair of limbs consists ot - Compare what we have said above (pp. 27, 28) about 



eight joints besides the coxa, but in this order it is not a the movability of the legs in Arachnida generally, 

 palpus, but a walking limb or leg. 



