DEVELOPMENT OF THE SKULL IN THE OSTRICH TEIBE. 145 



slit in the palate behind the solid part of the intcrmaxillaries. The prevomers are 

 very thin, and studded with small irregular fenestrse (Plate XII. fig. 2, p.v.). The 

 middle fork of the vomer has become less than the lateral ones in front (v.), the middle 

 of the bone has become higher, and the hinder forks still more divaricate. The 

 descending process of the nasal is nearly obsolete (Plate XII. fig. 1, n.); the broad 

 upper part has spread further over the upper ethmoid (Plate XTI. fig. 3, eth.). No 

 important change has taken place in the lacrymals (I.), but the frontals and parietals 

 (/'., p.) have become much more developed than in the nearly ripe chick. Even the 

 upper fontanelle (Plate XII. fig. 3) is nearly filled up ; but there are still two orbital 

 fontanelles, the orbital plate of the frontal being very narrow at present, but closely 

 adherent to its own cartilage — the orbito-sphenoid. 



Bromceus, " C." 



The third stage of the Emu's skull is that of a young of the freckled species (I), irro- 

 ratus), evidently about two months, or perhaps ten weeks old *. There is in this a 

 considerable advance on the la«t ; and as this skull was partly disarticulated by macera- 

 tion, I shall speak chiefly of the axial bones ; and it must be remembered that although 

 the two Emus are closely related species, yet some qualification must be made in the 

 comparison of stages of birds only generically the same. 



The triple nature of the transversely oval condyle of the occiput (Plate XII. fig. 6, o.c.) 

 is well seen, the lateral elements almost meeting on the upper surface of the mesial piece. 

 The basioccipital (Plate XIII. fig. 1, b.o.) ends much more bluntly forwards than in the 

 last, and is very thick as well as very broad ; it reaches out on each side in a sharp angle ; 

 the broad anterior margin makes the basitemporals diverge more than in the last. The 

 exoccipitals {e.o.) are very massive ; together they only form half the foramen magnum 

 (Plate XII. fig. 6.), more than a fourth of which is completed by the superoccipital {s.o.) 

 above. The opisthotic has still only half its suture (in the middle) obliterated (Plate XII. 

 fig. 6, op.); it has to be deducted from the exoccipital. The superoccipital forms a very 

 elegant crown to the occipital arch (Plate XII. fig. 6, s.o.); a blunt keel has appeared 

 on the mid line; within, half the anterior and most of the posterior vertical canals 

 (Plate XIII. fig. 4, a.s.c, p.s.c.) can be seen in its substance. 



The inner part of the opisthotic has not hastened to coalesce with the exoccipital 

 (Plate XIII. fig. 4, op.), and the small squarish epiotic (Plate XIII. fig. 4, ep.) is still 

 quite distinct. The exorbitantly large prootic (Plate XIII. figs. 1, 2, 3, & i, pro.) has 

 six irregular sides, and convexities and sinuosities without number. Below, it articu- 

 lates by a dentate suture with the basioccipital (b.o.), in front, by a similar suture 

 with the alisphenoid {a.s.). On the thick rounded upper surface the equally thick 

 parietal rests, whilst the outer scooped surface is shielded by the incudal splint (squa- 

 mosal), just hiding from view the extensive suture connecting it with the opisthotic 

 and the exoccipital (Plate XIII. fig. 2 shows these removed) ; above the opistliotic it 



* Lent me by Mr. Flower, the eminent articulator. 



MDCCCLiXVI. y 



