Figure 4. Serial sections through the head of Psilorhynchus. A, transverse section through the masticatory plate of Psilorhynchus sucatio, KU 40642, male, 48.6-mm standard length (SL). B, transverse section through the masticatory plate of Psilorhynchus balitora, KU 40375, 36.1-mm SL. C, sagital section through the lateral ethmoid of Psilorhynchus sucatio, KU 40642, 49.8-mm SL, inset image shows close-up of connective tissue between transverse shelf on medial face of infraorbital 2 and the ventral surface of the lateral ethmoid of a more medial section. D, sagital section through the upper jaw and ethmoid region of P. sucatio, KU 40642, 49.8-mm SL, inset image shows close-up of boxed area. E, sagital section through the upper jaw and ethmoid region of P. balitora, KU 40375, 29.9-mm SL, inset image shows close-up of boxed area. Abbreviations: Boc, basioccipital; CT, connective tissue; DA, dorsal aorta; E, esophagus; Ep, epidermis; IE, inner ear; IO2, inner ear; LE, lateral ethmoid; M, meniscus; MaPL, masticatory plate; Mx, maxilla; N, notochord; Pc, perichordal ossification of the basioccipital; PE, preethmoid; PT, pharyngeal teeth of ceratobranchial 5.