DEVELOPMENT OF THE SKULL IN THE OSTEICH TRIBE. 175 



bird comes so near the " Gallinse," which have this knob bifid, yet in the Tinamous it is 

 oval longitudinally, being an exaggeration of what exists in the Eails and even in Plovers. 

 The thick basal region of the skull {h.o., b.s.) is gently convex, and in T. robustus is also 

 slightly carinate anteriorly ; there are indeed four carinse, as in the Apteryx, the longi- 

 tudinal ridge being broken at the base of the rostrum, by a remnant of the pituitaiy 

 space (see Zool. Trans, vol. v. pi. 40, fig. 1, in which figure the converging lateral ridges 

 might be mistaken for the edges of the basitemporals, which in typical birds do meet at 

 that point). The eustachian canals are floored by bone for a very small space, and lie very 

 far apart at their exit — further apart than in some of the large Ostriches. The rostrum 

 of the basisphenoid (r.b.s.) is keeled in both species — most so in T. robustus, in which it 

 extends further forwards than in T. variegatus. The anterior pterygoid processes {a.p.) 

 are wider in the former than in the latter, but there is no evident difference in the pos- 

 terior outgrowths ; in both the spurs that often grow from the basitemporals are entirely 

 aborted. The extreme shallowness of the ear-drum, arising from the shortness of the 

 exoccipital wings (Plate XV. fig, 1, e.o.), is well shown in both ; the occipital plane agrees, 

 on the whole, with that of the Apteryx, but the edge of the parietals overhangs the super- 

 occipital instead of graduating insensibly into it (Plate XV. fig. 1). There is more bone 

 in the septum of T. variegatus than in that of T. robustus, but in the latter the presphe- 

 noid reaches the conjunction of the basisphenoid with the perpendicular ethmoid ; it 

 does not in T. variegatus (Plate XV. figs. 1 & 4, p.s.). In the latter the anterior sphenoid 

 stands in front of the orbital plates of the frontal ; in T. robustus it passes behind those 

 plates. In both there is a most unique display of sutures at this part, these being most 

 clearly seen in T. variegatus (Plate XV. figs. 1 & 3), although the bird (as Mr. Bartlett 

 informs me) was in its fourth year. In this bird the alisphenoid {a.s.) is distinct from 

 the frontal (/.) above, from the basisphenoid [b.s.) below, and from the orbito-sphe- 

 noid [a.s.) in front ; also from the postfrontal epiphysis at its supero-extemal angle {p-f.). 

 The extremely small presphenoid and orbito-sphenoids are still separated from their sur- 

 roundings by distinct sutures, the upper bar of the ethmoid (fig. 1, p.e.) nearly reaching 

 the alisphenoids, and nearly insulating the interorbital fenestra behind — a most unusual 

 abortion of the anterior sphenoid, as compared with the Mammal, the Eeptile, or even 

 with some of the Struthionids, but perfectly ornithic. The sagittal and lambdoidal sutures 

 (Plate XV. fig. 3) are thoroughly obliterated ; but the coronal suture (Plate XV. fig. 3) 

 is as completely open as in the Lizard, and joins that between the alisphenoid and 

 frontal on each side. In T. robustus the alisphenoid has joined itself to the basisphenoid 

 below ; the other sutures are the same, and the important coronal suture was not drawn 

 in my other paper because the skull was diseased at top ; afterwards I found the suture 

 thoroughly open at the sides, as in T. variegatus. This is only part of what is reptilian 

 in these birds ; and it is curiously in contrast with the very solidified condition of the 

 rest of the skull. In T. variegatus the suture between the high prepituitary portion of 

 the basisphenoid and the lower bar of the ethmoid is quite visible; and in both the 

 junction of the rostrum with the ethmo-presphenoidal plate can be seen, although anchy- 



