THE RELATIONSHIP OF THE CHELICERATE ARTERIAL SYSTEM ...

FIRSTMAN-CHELICERATE ARTERIAL SYSTEM AND ENDOSTERNITE 11cular membrane. A close examination showed that this is a histological continuity ofconnective tissue; the endosternite is morphologically a thickened portion of the perineuralvascular membrane. Four pairs of suspensor muscles insertontothe dorsal surfaceof the endosternite at its lateral margins, and two pairs insert onto the ventral surface.Transverse suspensors are lacking in all the opilionids I have examined.The suborder Laniatores includes, among other families, the Gonyleptidae, which isconfined in its distribution to Latin America (pers. comm., C. J. Goodnight). Fig. 7A andB shows that the gonyleptid possesses a perineural vascular membrane which is essentiallysimilar to that of a palpatorid; the endosternite, however, is considerably reduced, itsdorsal portion being represented by a thin, transverse band across the posterior end of thesubesophageal ganglionic mass. The reduced condition of the gonyleptid endosterniteclosely resembles that of the other nonpalpigrade apulmonates, and is accompained by'erineural vascular membranelearthindgutmoufhgenital orificeright cheliceraBleft odiferous gland orifice,perineural vascular membranedorsal suspensor of the endosterniteleft pedipalpaortaventral suspensor of the endosterniteendosterniteleft cheliceracoxaof leg 10.5mmFig. 8.-A: midsagittal view of a cyphophthalmid opilionid, Siro acaroides, seen from the left;B: lateral view of same, with part of the body wall removed so äs to expose the endosternite andsuspensor muscles on the left side. The central nervous system is shown with dark shading.