NO. 10 FnEDING ORGANS 01-" AKACH NIUA— SNODGRASS 4I 



surface overlianging the mouth and the inner end of the prcoral food 

 cavity. The mouth (E, G, Mtli) is a small unguarded aperture be- 

 neath the base of the labrum. I->om below the mouth there projects 

 forward the broad, basinlike floor of the preoral cavity (E) formed 

 of the endite lobes of the first leg coxae (IIIEiidt). Between the 

 mesal edges of these coxal lobes is a groove, which is closed below 

 by the closely applied endites of the second leg coxae (D, IVllndt), 

 and proximally runs into the mouth (E, Mth). The pedipalp coxae 

 are entirely separated from each other, and there is no recognizable 

 remnant of the pedipalp sternum in the scorpion. The broad, flat, 

 mesal surfaces of the coxae are mostly membranous (O, IICx), and 

 form the lateral walls of the preoral food cavity (D, PrC). An- 

 teriorly the coxae are produced into short coxal processes (cxp) 

 mesad of the trochanters. The coxal bases are connected by two thick 

 bundles of transverse muscle fibers, which pass through the labrum 

 (G, tnicl). These muscles occur in other arachnids, and are labral 

 muscles ; in the scorpion they appear to be operative on the pedipalp 

 coxae by reason of a union of the base of the labrum with the coxal 

 walls. 



The lobes of the first and second leg coxae (fig. 13 D, IIIEudt, 

 IVEndt) that form the lower lip of the scorpion, or floor of the 

 preoral cavity, are here termed cnditcs because they arise from the 

 l)ases of the coxae (F) and not frotn their distal ends as do the coxal 

 processes {cxp) of the pedipalp coxae. Coxal lobes of the same nature 

 occur also in the Phalangida. 



There is no prominent epislomal plate in the scorpion, but at the 

 base of the dorsal wall of the labrum is a strong, irregular scleroti- 

 zation (fig. 13 G, Epst), which clearly represents the epistome, since 

 on it are attached the dorsal dilators of the pharynx (did), and from 

 it is given off a pair of apodemal arms {cAp). 



The pharynx of the scorpion is a small, pear-shaped sack enlarging 

 upward and posteriorly from its narrowed etitrance at the mouth 

 (\\f^. 13 G, riiy). It is .somewhat comjjresscd laterally, rounded at 

 the inner end; the slender oesophagus (Oc) departs from the lower 

 wall at the end of a ventral channel from the mouth. The dorsal wall 

 of the sack is deeply infolded and the trough of the invagination is 

 strengthened by an elastic rod. Dilator muscles attached on the con- 

 cave dorsal wall (did) arise on the epistomal sclerotization (Epst) 

 at the base of the labrum, and lateral dilators take their origins on 

 the epistomal apodemes (cAp). Compressor muscles cover the lateral 

 walls of the pharynx. 



The sting of the scorpion appears to be an ai^pcndagc of the last 



