1902.] ANATOMY OF THK PEDIPALPI. 179 



From this arrangement may be derived that of Thelyphonus, as 

 ah'eady described (p. 175). 



In the Spiders the trough is formed by the median prosternal 

 plate (the labium or sternum of the first postoral somite) which 

 projects from beneath and beyond the mouth (text-fig. 43, D, lah. 

 p. 180). The space on each side between this plate and the cama- 

 - rostome is blocked by the coxa of the appendage of the second pair. 

 Within the order Aranese the simplest type of mouth-parts is found 

 in the primitive Mesothelfe and Mygalomorphae, where the cama- 

 rostome is high and short, and the coxee in question but little 

 modified. In the Arachnomorphse, on the contrary, the cama- 

 i^ostome is longer, depressed, and overlaps the labium, the two 

 being flanked on each side by a preaxial process from the coxa — 

 the so-called maxilla (text-fig. 43, C, D, cam., mx.j?., p. 180). In 

 more primitive forms the appendages of the fii^st and second pairs 

 (mandibles and palpi) are freely movable, and the labium is 

 separated from the rest of the sternum. But in certain other 

 forms the labium and basal segments of the palpi are fused to 

 the sternum, the maxillary processes meet in front of the labium, 

 and the mandibles are mesially hinged together and susceptible 

 of but little movement ; the five sclerites in question, together 

 with the camarostome which they completely enclose, constituting 

 a highly specialized " proboscis," equal in complexity to that of 

 many Acari. 



Viewed from above, the mouth-parts of the Pseudoscorpiones 

 (Garypus) much resemble those of Tlielyphonus and the Spiders. 

 The camarostome is long, porrect and, as in Thelyphomis, fused 

 dorsally on each side in its basal half to the adjacent preaxial 

 surface of the coxa of the 2nd appendage (chela), which projects 

 forwards on each side of it. Distally, it ends in a subeylindiical 

 fleshy lobe which reaches to the end of the membranous sterno- 

 coxal (maxillary process) of the coxa (text-fig. 42, D, c«m., inx.p., 

 p. 177). Inferiorly, however, instead of being uniformly convex, 

 it is deeply grooved longitudinally, the groove giving rise to a 

 pair of lips, a right and a left. Projecting forwards into the 

 groove between these two lips is a compressed and pointed pro- 

 sternal or labial prolongation, which arises at its basal end from 

 the inferior part of the area between the juxtaposed proximal 

 ends of the preaxial surfaces of the coxee (text-fig. 42, D, lah., 

 p. 177). These coxse meet, without fusion, in the middle line 

 beneath the prosternal process, and form, as in Thelyjjhonus, a 

 trough to prevent the escape of fluid ; the labivim (jorosternum), 

 which, like the lips of the camarostome, is thickly hairy, con- 

 stituting a kind of tongue-like organ ' , above their line of meeting ) 

 In the Podogona or Ricinulei {Cryptostemma) and most (?all) 

 Acari the suboral trough results from the union of the coxa? of 

 the palpi beneath the camarostome. 



In the Solifugfe (Galeodes) the "beak" is quite peculiar. It 

 consists of a horizontally porrect tubular proboscis, bearing the 



1 See Croneberg, Arch. f. Nat. 1880. 



12* 



