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 ARACHNIDA 543 killed material, and is imperfectly known, though the presence of narrowed in front; the appendages of the 1st pair small, much the coxal glands was determined by Macleod in 1884. The pro- narrower, taken together, than the posterior border of the carapace. portionately enormous chelse (chelicene) of the first pair of appendages Serrula on movable digit of appendages of 1st pair fixed throughare not provided with poison glands ; their bite is not venomous. out its length, and broader at its proximal than at its distal end ; Galeodes has been made the means of a comparison between the the immovable digit with an external process. structure of the Arachnida and Hexapod insects by Haeckel and Family—Cheliferidse (Chelifer (Figs. 66, 67, 68), Chiridium). other writers, and it was at one time suggested that there was a ,, Garypidse {Garypus). Sub-order b. Hemictenodactyli.—Dorsal plate of prosoma scarcely narrowed in front; the appendages of the 1st pair large, not much narrower, taken together, than the posterior border of the carao prce-gen 12 3 Opisthosoma Prosoma Fig. 69.—Galeodes, sp., one of the Solifugie. I to VI, the six prosomatic limbs cut short; o, the eyes; ft, c, demarcated are*, of the cephalic or first prosomatic plate corresponding respectively to appendages I, II, III and to appendage IV (see Fig. 68); d, second plate of the prosoma-carrying appendage V; e, third plate of the prosoma-carrying appendage VI. The praegenital somite is absent. 1, first somite of the opisthosoma ; 2, second do.; 8, prosomatic tracheal aperture between legs IV and V ; S' and 8", opisthosomatic tracheal apertures; 10, tenth opisthosomatic somite ; an, anus. (Original.) genetic affinity between the two groups — through Galeodes, or extinct forms similar to it. The segmentation of the prosoma and the form of the appendages bear a homoplastic similarity to the head, pro-, meso-, and meta-thorax of a Hexapod with mandibles, maxillary palps and three pairs of walking legs; whilst the opisthosoma agrees in form and number of somites with the abdomen of a Hexapod, and the tracheal stigmata present certain agreements in the two cases. Reference to literature (36). Order 6. Pseudoscorpiones — Chelonethi, also called Chernetidia (see Figs. 70, 71, 72).—Prosoma covered by a single dorsal shield, at most furnished with one or two diplostichous lateral eyes ; sternal elements obliterated or almost obliterated. Appendages of the 1st pair bisegmented completely chelate, furnished with peculiar organs, the serrula and the lamina. Appendages of 2nd pair very large and completely chelate, their basal segments meeting in the middle line,

Fig. 72.—Garypus litoralis, one of the Pseudoscorpiones. Lateral view. I to VI, basal segments of the six prosomatic appendages ; o, eyes ; pree-gen, tergite of the prse-genital somite ; 1, genital or first opisthosomatic somite ; 2, 3, 10, the second, third, and tenth somites of the opisthosoma ; 11, the minute eleventh somite ; an, the anus. (Original.) pace. The serrula or the movable digit free at its distal end, narrowed at the base; no external lamina on the immovable digit. Family—Obisiidfe (OMsium, Pseudobisium). ,, Chthoniidse (Chthonius, Tridenchthonius). Remarks.—The Book-scorpions—so called because they were, in old times, found not unfrequently in libraries—are found in rotten wood and under stones. The similarity of the form of their appendages to those of the scorpions suggests that they are a degenerate group derived from the latter, but the large size of the prse-genital somite in them would indicate a connexion with forms preceding the scorpions. Reference to literature (37). Order 7. Podogona = Meridogastra (see Figs. 73 to 76).—Dorsal area of prosoma furnished with two shields, a larger behind representing, probably, the tergal elements of the somites, and a smaller in front, which is freely articulated to the former and folds over the Fig.73.—Cryptostemma Karschii, one of the Podogona. Dorsal view of male, enlarged five times linear. Ill to VI, the third, fourth, fifth, and sixth appendages of the prosoma ; a, movable (hinged) sclerite (socalled hood) overhanging the first pair of appendages; 6, fused terga of the prosoma followed by the opisthosoma of four somites; an, anus; E, extremity of the fifth appendage of the male modified to subserve copulation. (Original drawing by Pocock and PickardCambridge.)

F ig. 70.—Garypus litoralis, one of the Fig. 71.—Garypus litoralis, one of Pseudoscorpiones. Ventral view. I to VI, the Pseudoscorpiones. Dorsal prosomatic appendages; o, sterno-coxal view. I to VI, the prosomatic process of the basal segment of the appendages ; o, eyes ; prce-gen, second appendage ; 1, sternite of the pree-genital somite ; 1, tergite of genital or first opisthosomatic somite ; the genital or first opisthosothe prat-genital somite, though repre- matic somite ; 10, tergite of the sented by a tergum, has no separate tenth somite of the opisthosoma; sternal plate; 2 and 3, sternites of the 11, the evanescent eleventh second and third somites of the opistho- somite of the opisthosoma ; an, soma, each showing a tracheal stigma; anus. (Original.) 10 and 11, sternites of the tenth and eleventh somites of the opisthosoma ; an, anus. (Original by Pocock and Pickard-Cambridge.) as in the Uropygi, and provided in front with membranous lip-like processes underlying the proboscis. Appendages of the 3rd, 4th, 5th, and 6th pairs similar in form and function, tipped with two claws, their basal segments in contact in the median ventral line. The prse-genital somite wide, not constricted, with large tergal plate, but with its sternal plate small or inconspicuous. Opisthosoma composed, at least in many cases, of eleven somites, the 11th somite very small, often hidden within the 10th. Respiratory organs in the form of tracheal tubes opening by a pair of stigmata in the 2nd and 3rd somites of the opisthosoma. Intromittent organ of male beneath sternum of the 1st somite of the opisthosoma. Sub-order a. Panctenodactyli.—Dorsal plate of prosoma (carapace)

appendages of the 1st pair. Ventral area without distinct sternal plates. Appendages of 1st pair, tri-segmented, completely chelate. Appendages of 2nd pair, with their basal segments uniting in the middle line below the mouth, weakly chelate at apex. Appendages of 3rd, 4th, 5th, and 6th pairs similar in form; their basal segments in contact in the middle line and immovably welded, except those of the 3rd pair, which have been pushed aside so that the bases of the 2nd and 4th pairs are in contact with each other. A movable membranous joint between the prosoma and the opisthosoma, the generative aperture opening upon the IV in i g. 74. — Cryptostemma Karschii. anterior aspect of the prosoma with the “ hood ” removed. I to IV, first to fourth appendages of the prosoma; a, basal segment of the second pair of appendages meeting its fellow in the middle line (see Fig. 75). (Original drawing by Pocock and Pickard-Cambridge.) II a ventral side of the membrane. Prae-genital somite suppressed ; the opisthosoma consisting of only four visible somites, in addition to a tubular ring round the anal orifice. Respiratory organs unknown. Intromittent organ of male placed at the distal end of the appendage of the 5th pair. Family — Cryptostemmidse {Cryptostemma) {*Anthracomartus) Carboniferous. Remarks on the Podogona.—The name given to this small but