DEVELOPMENT OF THE SKULL IN THE OSTEICH TEIBE. 149 



and the interior of the bone is being absorbed on one side, whilst it is only forming on 

 the other. The articular cartilage is carefully wrapped in its splints before ossification 

 commences ; when their model is fully ossified, then they coalesce to a great extent. 



Bromceiis, "D." 

 My fourth specimen of the Emu was put into my hands in an unmacerated condition 

 by Mr. Bartlett ; it had died on its voyage from Australia, and was of the freckled kind 

 {Dromceus irroratus, Scl. and B.). This individual was but little older than the last, yet 

 some important changes have taken place ; there are also some individual differences ; 

 and besides this, as it was in a fresh state, I ^m able to give drawings and descriptions of 

 the complex nasal cartilages. The cranial part is very high, and smoothly ovoidal; 

 indeed its form is such as is found in the young of the Great Ostrich when the entire 

 chick is no larger than a sparrow, Struthio, " A ;" the frontal convexities over the 

 hemispheres have a peculiar fcetal character, although the bird was fully half the size 

 of the adult. In respect of its roundness this skull comes near that of the Apteryx ; 

 but that which distinguishes the latter bird is the great size and breadth of the occi- 

 pital region as compared with the rest of the skull, a character which it shares with the 

 lowest monotrematous and placental Mammals, e.g. Echidna, Ornithorhynchus, Sorex, and 

 Talpa. In this specimen of B. irroratus the basisphenoidal rostrum is deeper and more 

 cultrate than in the last, and there is a more marked remnant of the pituitary space ; 

 the basitemporals do not converge so much, and consequently the occipito-sphenoidal 

 synchondrosis is better seen below. 



The postfrontal is scarcely more developed, being almost entirely cartilaginous, and 

 the descending plate of the presphenoid is still soft. The orbito-presphenoidal bone 

 began at the top, in the skull-floor ; the high part of the basisphenoid and the vertical 

 ethmoid are still far apart. The ethmoidal "fenestra" is divided into two by a broad 

 periosteal bar of bone, leaving only a small space membranous above and below. 



The delicate maxillary style has partly coalesced with the styloid angular process of the 

 intermaxillary; but for the early specimen its existence could not have been proved. The 

 palatine fenestra has become definite ; it is oval, and about ^th of an inch in diameter. 

 The pterygoid is very flat, splintery, and unlike the elegant terete bone of the typical 

 birds. The height of the intermaxillary in front, and the strength and form of the 

 whole bone, reminds one strongly of the same part in Dinomis rohustus, and especially 

 of the subgeneric form, Palapteryx (Zool. Trans, vol. iii. pi. 54, where in fig. 1 the 

 intermaxillary fragment is placed considerably too far from the skull). The os quadra- 

 turn is a marvellously swollen clumsy bone, totally unlike its homologue in the most 

 gigantic of the Rails — the mis-called JXnornis casuarinus (op. cit. pi. 62). As in the 

 Blackbird (Turdus nierula), the base of the stapes is perforate like that of the Mammal; 

 this is caused by its having a large pneumatic hole on one side and a lesser passage on 

 the other ; the apex has a triradiate piece of cartilage growing from it. 



The edges of the upper ethmoidal bone have not descended far into the aliethmoidal 



