Antennw and Mandibles 25 



absent only in the genus Siro (PI. V., fig. 1 c). On the outer edge of the under suiface a 

 process is found (our "processus inferior exterior") (PI. I., tig. If, c) which varies in shape, being 

 sometimes more conical, in other cases rather compressed ; it is connected with the ridge on 

 the dorsal side by means of a low transverse ridge on the outer side. In Pettalus cirm- 

 ciformis Cambr. (PL III., fig. 2 h) processus inferior exterior is very little developed, and it is 

 wanting in Ogovia (PI. II., fig. 6 a). The under surface of the basal joint generally carries a 

 conical rounded process near the base (our " processus basalis") (PI. I., fig. 1 /, h), which bemg 

 thick occupies nearly the whole width of the under side (PI. III., fig. 3 c). This is not found 

 in Siro, Ogovia, and Parasiro. As we have mentioned before, the basal portion of the first 

 joint is more or less hidden by the anterior edge of cephalothorax, which often projects in 

 the shape of a collar. On the inner side the base of the first joint exhibits a proportionately 

 large triangular prolongation (PI. I., fig. 1 /, a), to the posterior corner and along the posterior 

 margin of which the lowering muscle (??i') of antenna; is fixed ; from this line it extends 

 forwards and upwards in a slanting direction, and works consequently at a very favourable angle. 

 The lifting muscle of antennae {m"), which is much weaker, is fixed to the uppermost corner 

 of the base of this prolongation and stretches from that point backwards, almost horizontally ^ 

 The membrane connecting antenna; and cephalothorax forms a fold round the triangular pro- 

 longation of the basal point. 



In accordance with the great length of antennae their second joint forms a rather acute 

 angle with the first joint when at rest. The statement of Joseph in speaking oi Siro duricorius 

 (a, p. 247), "when excited it stretched the chelicera; straight out, with the fingers spread...," 

 implies that the animal is able to straighten its antennae entirely. The second joint varies 

 not a little in shape. In those genera which, like Siro (PI. V., figs. 1 c and 1 d) and especially 

 Parasiro (PI. V., figs. 2 h and 2 c), have less elongated antenna, the second joint is nearly 

 fusiform, and the thickest point of it is on the distal side of the middle ; but where antennae 

 are long and slender, as in Stylocellus and Pettalus (PL I. — III., several figures), the joint is 

 less distinctly fusiform and has its greatest thickness at a point clearly on the proximal side 

 of the middle. 



We also notice a certain correlation between the width of stomotheca and the shape of 

 antennae. In all Cyphophthalmi the apical portion of antennas when at rest is drawn into 

 stomotheca, which accordingly i.s broader, when the apical portion of antennae is comparatively 

 robust, than when this is slender. The chela formed by the third joint in conjunction with 

 the prolongation of the second joint is considerably shorter and more slender in those which 

 have slender antenna; than where these are more robust ; the edges of the bi'anches of the 

 chela, which are opposed to each other, are armed with a row of teeth, of which the number 

 and shape differ in different genera. 



Mandibulw (maxilte auctorum) (PL I., figs. 1 i— 1 /.:' ; PL IV., fig. I f—l g ; PL V., fig. 1/). 



The basal joint of the second pair of limbs forms the mandibles as in all Arachnida, where 

 such are found I It consists of two distinct portions, a basal pars palpigera (PL I., fig. I j, p), 

 and an apical pars mandibularis (m). Of the latter we shall speak in treating of the structure 

 of the mouth. The pars palpigera is prolonged into a conical prominence which carries 

 palpus. The latter consists, as in Opiliones generally, of five joints, and the general structure 



' The same muscular arrangement is met with in Lania- ^ Palpigradi (Koenenia Grassi) have no mandibles, 



tores (Sorensen, b. Tab. i. fig. 3). 



s. 4 



