198 



Charles Searing Mead. 



the mammals. The highly fenestrated character of the side wall in 

 the reptilian chondrocrania is undoubtedly a secondary acquisition, 



I. par. 



fcn.s.p. 



rf car. thy. 



- <\^/) ^ 



Fig. 8. Section through the anterior portion of the otic region just in 

 front of the ear-capsules, showing a vestige of the primitive side wall of the 

 brain, the processus clinoideus posterior p.c.p., and the deep narrow anterior 

 portion of the basal plate h.p. The outer ends of the processi clinoidei 

 posteriores are connected with the ear-capsules, x 1^- 



IV, nervus troehlearis ; JIL nervus oculomotorius ; g.semi., ganglion semi- 

 lunare (Gasseri) ; hyp., hypophj^sis ; VI., nervus abducens; n.p.s.m., nervus 

 petrosus sqperficialis major (palatine branch of the facial) ; g.ot., ganglion 

 oticum ; ch.ty., chorda tympani ; VII, nervus facialis, motor branches ; car.thy., 

 thyroid cartilage; thy., thyroid gland; hyo., hyoid arches, coruu hyale above 

 and cornu branchiale I below ; M. c, Meckel's cartilage ; fcn.s.p., fenestra 

 spheno-parietalis ; l.par., lamina parietalis ; pa., anlagen of parietal bone. 



and not at all in the line of mammalian evolution. In Lepus and 

 Talpa this commissure is only a narrow bridge of cartilage, while in 



