CHONDROCEANIUM 



311 



Fig. 155. — Illustrating the development of the chondrocranium in Lung-fishes. 

 (After Agar, 1906.) 



A, Protopterus, stage 31 ; B, LepicUmren, stage 34 ; C, Lepidosiren, stage 38. a.c, auditory capsule ; 

 g.r, floor of Gasserian recess ; Hy, hyoid arch ; i.o, interopercular ; me, mesethmoid ; M, mandibular 

 arch; N, notochord; o, opercular; oca, occipital arch; oc.r, occipital rib; o.p, occipital plate; o.*, 

 orbito-temporal ; p.g, pectoral girdle; P.O. position of Pinkus's organ ; p.q, palatoquadrate ; Q, quad- 

 rate ; s.n.c', subnasal cartilage ; I, first branchial arch ; III, foramen for Oculomotor ; V, VII, foramina 

 for Trigeminal and Facial. 



