STUDIES ON THE ARACHNID BNTOSTEBNITE. 261 



dorsal side wiili eiitosternite in situ to show tiie muscles radiating to the 

 post-oral appendages II to VI, the anterior longitudinal muscles wiiich pass 

 from an entosclerite above tiie rostrum to tiie extremities of the anterior 

 cornua, and the longitudinal muscles which pass backward into tiie pregenital 

 somite. 



Fig. 18. — Lateral view of eiitosternite of tiie same, with the four dorsal {Itg. 

 to 4(7.) and four ventral (1*^. to Is/.) apophyses, and tiie tendon running 

 forwards from the first ventral apophysis to the prosternum. 



Fig. 19, — Ventral view of the same, sliowing the arrangement of the four 

 ventral apophyses in a circle round the pharyngeal notch. 



Fig. 20. — Entosternite of Palamnae us Tliorelli, with tiie posterior flap or 

 diapliragiu removed, showing the fibro-muscular attachment of the anterior 

 cornu to tiie coxa {ex.) of tlie fourtli appendage ; cr., lateral processes repre- 

 senting the muscle-bearing crest seen in Thelyphonus; 4/^., ^i(/., anterior 

 and posterior pair of dorso-veutral muscles, the suggested homologues of the 

 apophyses numbered ^tg. and 5/y. in the eiitosternite of Thelyphonus 

 (PI. 13, fig. 2), and representing in all probability the tergo-sterual muscles of 

 the fifth and sixth somites of the prosoma ; F.P., median process of subneural 

 arch dividing into a pair of apophyses ; Da., median dorsal portion of " body " 

 of entosternite forming the roof of the neural canal. 



Fig. 21. — Entosternite of one of the Vejovidse (lurus dufoureius), wiiii 

 posterior flap {P. F.) or diaphragm attached, to show its correspondence in 

 origin with the lateral crest {Cr.), and its median perforations for the gut {Al.C.) 

 and aorta {Aoc), between which lies the channel for the lodgment of the aorta, 

 formed by the dorso-ventral muscle of the second pair {htj.) and a strip of 

 connective tissue, which binds the right and left portions of the diaphragm 

 together. 



Fig. 22. — Entosternite of Bothriurus bonarieusis, showing the re- 

 duction of the median dorsal portion of the "body," forming the roof of the 

 neural canal, to a narrow transverse bar [Da.). 



Fig. 23. — Anterior view of entosternite of the same, showing the neural 

 canal {N. 6'.), dorsal arch {Da.), and subneural arch {Sa.). 



Fig. 24. — Entosternite ofCeutruroides margaritatus, with most of the 

 diaphragm removed, showing the lateral compression of the " body " or dorsal 

 arch {Da.) of the neural canal, the juxtaposition of the second pair of dorso- 

 ventral muscles (5/j/.), and the tips of the apophyses of the median jirocess 

 of the subneural arch {f^.F.). 



Fig, 25. — Entosternite of the same, wilh its dorsal portion removed to show 

 the cut ends of the lateral walls {La.) of the neural canal, the floor (6«.) of 

 the latter and the median process terminating in two expanded fan-shaped 

 apophyses {V.F.). 



Fig. 20. — The so-called entosternite of Solpuga sagittaria, cleaned 



