COMPAEATIVE MORPHOLOGY OF THE GALEODID.^i. 321 



Along the anterior surface of each coxa there is a secondary fold which projects 

 internally and forms a solid buttress ; round the distal points of these buttresses the 

 limbs rotate (PI. XXYIII. fig. 15 b). 



This support is especially strengthened in the case of the 5th limb, which has probably 

 to work upon or sweep round the body more actively than either the one in front of it 

 or that behind it. 



These buttress-like supports to the limbs appear to be a feature common to all the 

 Arachnids ; the folding-in of the cuticle to form them is visible to the naked eye on the 

 anterior faces of the coxa3 of any large Spider or Scorpion. 



There are similar buttresses for the support of the chelicera?, each of which thus also 

 rotates round a single solid point. Their position is, however, remarkable. They occur 

 latei-ally inside the cephalic lobes and under the remarkable areas found at each side 

 of the " head " iu all the Galeodida? (PL XXVII. figs. 1, 3, 6, 7 a). I at first thought 

 that these areas were the remains of the coxse of the chelicerse (cf. Pocock, 6o). If 

 so, these buttresses might be homologous with those of the other limbs. But, as will 

 be more fully explained in the section on the limbs, the evidence is rather in favour 

 of these particular buttresses being independent formations (see below). 



III. The Limbs. 



The limbs of Galeodes have been so often fiu'ured and described that no detailed 

 account of them is required here. We therefore confine ourselves to points which are 

 either new or else of special ruorphological interest. 



The Chelicerce. — The chelicerae in Galeodes are two-jointed, having, in addition to the 

 shaft, a ventrally-placed movable segment. 



There is strong reason for believing that this limb, in all Arachnids, was originally 

 three-jointed. We find, for instance, three joints in Scorpio and in the Phalangidse. 

 The two-jointed condition is therefore due to secondary loss of one joint. 



On the inner face of the chelicerse of Galeodes (PL XXVII. fig. 11) we find a very 

 clearly marked area wiiich, on comparison with the corresponding limb of Scorjoio, is to 

 all appearance the remains of a former proximal joint {cf. PL XXIX. fig. 1, b', d). On 

 the outer side, but belonging to the cephalic lobes, there is the curious cuticular area 

 (PL XXVII. fig. 1 a) characteristic of the Galeodida;, Avhich Pocock thinks may perhaps 

 also be part of the lost proximal joint. In support of this view, it must be noted that 

 under this sclerite, and as a fold of it, there occurs the buttress-like support to the limb, 

 like the buttress-supports in the coxse of the other legs. In spite of this fact, however, 

 this homology does not commend itself, for the following reasons : — 



In the first place, this buttress-support of the chelicerte can hardly be the homologue 

 of the buttresses in the coxae of the other limbs, inasmuch as its position in that case 

 would be difficult to explain. The two anterior pairs of limbs have been simply folded 

 forward, the chelicerse above, and the pedipalps below or at the sides of the mouth, so 

 that the anterior surfaces of their coxa3 face one another towards the median plane. 

 The homologue of the buttress-folds ought, therefore, to be fouad along the coxal areas 



SECOND SERIES. — ZOOLOGY, VOL. VI. 43 



