NO. lO FliEDING ORGANS OF AKACMNIDA — SNODGRASS 33 



fully or clearly described by Hansen and Sorensen from tbc single 

 specimen at their disposal. A transverse "crest," concave dorsally, is 

 said to be susi)ended from the united i)edipalp coxae ("mandibles") 

 and epistome, which is perforated by the oesophagus. I-'rom this wc 

 may suspect that there is here a structure resembling that in the 

 Thelyphonidae. Muscles of the oesophagus and pharynx, according 

 to Hansen and Sorensen, arise on the epistome ("pars basalis"), and 

 also "muscles attached to the base of the i)ars apicalis." The last 

 suggest the cpistomal muscles inserted into the base of the labrum in 

 Mastigoprocfus (fig. 9 D, Ibnucl). 



VI. THE CHELONETHIDA. OR PSEUDOSCORPIOXID.\ 



The external anatomy of the pseudoscorpions, together with the 

 resjMratory system and the reproductive organs, has been described 

 in great detail by Chamberlin (1931), and full accounts of the 

 external and internal structure are given in the comprehensive works 

 of Kastner (1927), Beier (1932), and Roewer (1936). The struc- 

 ture of the chelonethid feeding apparatus was correctly known to 

 Croneberg (1888), and the external mouth parts are well portrayed 

 by Pocock (1902). The information here given is taken mostly from 

 these sources. 



The conspicuous feature of the pseudoscorpions is the great relative 

 size of the chelate pedipalps (fig. 11 A). The chelicerae (Chi) are 

 small, two-segmented, and project straight forward from beneath the 

 edge of the carapace. Below the chelicerae is a group of structures 

 that constitute the mouth parts, including the labrum (I-tu) above, 

 a narrow under lip (Ipg) below, and anterior processes of the jjedipalp 

 coxae (IICx) on the sides. The coxae of the pedipalps, as those of 

 the legs, are almost contiguous along the midventral line of the body, 

 being separated only by a narrow membranous space in which are no 

 remnants of segmental sternal plates. The coxae themselves thus 

 replace the sterna and become the actual ventral exoskelcton of the 

 prosoma. 



The chelonethid chelicerae (fig. 11 B, E) have an unusually 

 elaborate structure, because, as Chamberlin (1931) pf>ints out, they 

 are used for several specific purposes besides that of holding the prey 

 during feeding. The pincers serve for carrying sand grains or other 

 material used in nest-building, the movable finger gives exit to a silk- 

 producing gland, and bears usually a spinneret near its apex ; the 

 chelicerae, furthermore, serve as cleaning organs, in adaptation to 

 which function the fingers arc equipped with membranous folds, 



