NO. 10 IKKDIXC OK(..\N> OK AKAi 1 1 N II i A -SNOIK'.RASS 43 



the postabdomen are likewise strongly niusculated, each being provided 

 with a single wide dorsal muscle with an axial tendon, a lateral muscle 

 on each side, and in addition a large median ventral muscle. 



The venom of the scorpion is produced in two sacklikc glands 

 contained within the swollen basal part of the sting (fig. 14 D, Gld). 

 'i'he glands have individual ducts opening separately near the point 

 of the sting through two lateral pores (E, I'Pr), from which grooves 

 extend to the tip. Each gland is closely invested along the entire length 

 of its mesal and dorsal surfaces by a thick muscular sheath made uj) 

 of several layers of semicircular fibers (D, F, nicls), attached dorsxilly 

 on the upper part of the lateral wall of the containing capsule, and 

 ventrally on the lower wall. Contraction of the muscles evidently 

 compresses the gland sacks against the rigid capsular walls. 



The scorpion is certainly not a primitive arachnid, though an an- 

 cient one. //, therefore, the scorpions have any relationship to the 

 extinct Eurypterida, the theor}- of \'ersluys and Demoll (1920), in- 

 sofar as it derives the eurypterids from primitive scorpions, would 

 appear to be more reasonable than the reverse. That the Xiphosurida 

 have a scorpion ancestry, however, is difficult to believe, considering 

 their primitive method of feeding and their evident relation to the 

 trilobites. 



VIII. THE PH.\L.\XGID.\, OR OPILIONES 



The Phalangida are characterized by the presence of lobes arising 

 from the bases of the coxae of the pedipalps and the first two pairs 

 of legs. Because of their position on the coxal bases these lobes of 

 the phalangiids are analogous to the lobes on the second and third 

 leg coxae of the scorpions, which, as explained in the last section. 

 are here termed cnditcs to distinguish them from the distal processes 

 of the pedipalp coxae in other arachnids. The jiedipalp endites of 

 the Phalangida are always closely associated with the mouth, and have 

 the appearance of a pair of jaws; they may be prehensile, but they 

 have no masticatory function, and hence are not appropriately termed 

 "manducatory" lobes. The first leg endites in the Phalangiidae re- 

 semble the pedipalp endites and are likewise associated with the mouth, 

 but the endites of the second legs never have a direct relation to 

 feeding. In the Cyphophthalini and the Laniatores the coxal endites, 

 whether hard or soft in texture, are immovably fixed on the coxae, 

 but in the Palpatores they are flexibly attached to the coxae, and 

 become indei)endently niovabk- Ijecause some of the body muscles of 

 the coxae are attached on liu-ir bases. .V labrum is always present, 



