168 ME. W. K. PAEKEE ON THE 8TEUCTUEE AND 



general nature of the Cassowary. The study of the structures of these vertebrates, in 

 which differentiation or segmentation is imperfectly performed, will be found to be 

 fraught with the richest results to morphology. The anterior nares (a.na.) are mere 

 low-lying slits, gradually widening in front ; the middle nares (Plate XIV. fig. 2, m.na.) 

 are large, suboval, and perfectly struthious, being greatly severed by the intrusion of 

 the over-large vomer (v.). The curious inferior turbinal hook is the continuous homo- 

 logue of the distinct lower antorbital piece of certain birds, e. g. " Musophaginse," 

 " Larinse," " Procellarinae," &c. 



The visceral rays are very variously developed as usual, the first prestomal being never 

 other than continuous with the skull base ; and already at this stage the anterior (pre- 

 nasal) half has waned into a mere thread. 



The posterior half of the larval intermaxillary is the thick swollen base of the 

 internasal cartilaginous plate (Plate X. fig. l%,s.n.); and there is never any line of 

 distinction between this wall, which, as a continuation of the ethmo-presphenoidal 

 cartilage divides one nasal labyrinth from the other, and the double (trabecular) 

 foundation on which it rests. The primordial part of the palatine apparatus — the 

 second pair of prestomal bars — is as simple as usual, there being only the palatine and 

 pterygoid (Plate XIV. fig. 2, pa., pg.) bones, answering to the pier of the arch only. 

 The former is almost horizontal ; the inner proximal edge, the anterior point of which 

 is attached to its true basis (the lateral ethmoid), lying a little higher than the thick 

 outer edge of the bone. The oblique sutural line between the palatine and pteiygoid 

 is of great extent, the former bone passing nearly to the end of the latter, this bone 

 (the pterygoid) also running along the whole inner margin of the palatine. Anteriorly 

 the external margin of the palatine fits, by harmony, with the inner edge of the pre- 

 vomer {p.v.), this almost confused interlocking of primary with secondary bones being 

 a constant thing in the structure of the facial arches. The front edge of the broad. part 

 of the palatine, bounding the middle nasal opening, is sharp and toothed ; the exter- 

 nal margin of the bone is sinuous, the front spur turning inwards, whilst that which 

 clamps the pterygoid curves a little outwards ; below, the broad part of the bone is 

 scooped, making the middle nostril deeper. The pterygoids have thek usual struthious 

 form, being thick behind, where the quadrate and sphenoidal facets are placed, and thin 

 and splintery in front, where the " mesopterygoid " becomes segmented off in other birds. 

 The great visceral arch, the fii'st poststomal or mandibular, has nothing very remark- 

 able about its primordial structures ; this is to be said, however, that the quadrate 

 (Plate XIV. figs. 1-3, g.) is not so cumbrous a bone as in the Emu, the metaptery- 

 goid process (not quite ossified) being rounder and smaller ; the oblong upper condyle 

 stands on a longer neck than is usual, and the body of the bone is more compressed 

 from before backwards ; there is already a wind-passage in the flat hinder face of this 

 bone (Plate XIV. fig. 2, q.). Ossification has commenced in the articular head of 

 Meckel's cartilage (Plate XIV. fig. 4, ar.), which has scarcely begun to shrink ante- 

 riorly, although nearly buried in the splints. 



