30 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 1 10 



the floor of the trough of the united coxae. The dorsal wall of the 

 labrum (Lm) is a mass of spongy but dense tissue, so thick that it 

 reduces the haemocoele of the labrum to a narrow slit (IHcl) con- 

 centric with the lumen of the food passage (PrC) below it. Pocock 

 (1902) says the cavity of the labrum ("camarastome") "is filled 

 for the most part with muscles which pass from its roof to its floor," 

 but he evidently was mistaken as to the nature of the tissue in the 

 labrum, and he must have missed the narrow haemocoele in its lower 

 part. An anterior bundle of muscle fibers from the epistomal apodeme 

 (D, Ibrmcl), however, does attach to the posterior end of the thick 

 dorsal wall of the labrum and merges into its spongy tissue. Behind 

 the base of the labrum, the lamina dorsalis and the lamina ventralis 

 are united along their upper edges (H), so that the food passage 

 between them {PrC) becomes a closed cavity. 



When this structure is seen from the side (fig. 9 D) or from below 

 (E), the lamina ventralis of the food passage appears as a large, 

 strongly convex, ovate body (Imv) firmly suspended from the median 

 edges of the dorsal plates of the pedipalp coxae (E, dplcx). The 

 wide posterior end of the lamina ventralis narrows into a long, free, 

 tapering arm (Phy), which is the ventral wall of the sucking part of 

 the ingestion apparatus, and is therefore the ventral plate of the 

 pharynx. The lamina dorsalis (F) has a form similar to that of the 

 lamina ventralis upon which it is closely superposed. Its anterior 

 margin bears a fringe of long hairs guarding the slitlike opening of 

 the food passage above mentioned ; its posterior part tapers into the 

 dorsal plate of the pharynx. The two plates of the pharyngeal region 

 are connected by infolded lateral membranes (I) allowing of expan- 

 sion and contraction. Dorsal dilator muscles of the pharynx (D, I, 

 did) arise on the epistomal apodeme (D, eAp) ; lateral dilators (dll) 

 arise on the basal apodemes of the pedipalp coxae (D, E, cAp). In- 

 asmuch as the pharyngeal plates of Mastigoproctus are directly con- 

 tinuous from the dorsal and ventral plates of the prepharyngeal food 

 passage, the so-called pharynx is dififerentiated from the latter only 

 by its expansible lumen and the possession of dilator muscles. 



No functional explanation can readily be given for this curious 

 ingestion apparatus of the Thelyphonidae. In a preserved specimen 

 the dorsal and ventral plates of the prepharyngeal section are in close 

 apposition, and there appears to be here no mechanism for expansion. 

 Certainly nothing but liquid could be sucked through the passage, and 

 the fringe of hairs at the entrance on the lamina dorsalis must effec- 

 tively keep out food particles. The thelyphonids feed on insects and 

 other terrestrial arthropods. They are said to seize and crush their 



