MORPHOLOGY OP OPISTHOCOMUS CRISTATUS. 67 



throughout by one bony ectostosis. Down below, among cartilaginous and semi- 

 cartilaginous fishes, e. (/. the Skate and the Sturgeon, the suprascapula is a distinct 

 segment of cartilage {op.clt. pi. i.). In the Amphibia Urodela this part is not seg- 

 mented off, but it remains unossified [ibid. pis. iii., iv.) ; in the Anura, however {ibid. 

 pis. v.-vii.), the suprascapula is semi-segmented from the scapula and has its own 

 ectostosis and endostosis. In the Lacertilia {ibid. pis. viii.-xi.) the suprascapula has 

 its own endosteal tract, but no outer plate of bone ; moreover, the cartilage between 

 the two regions is not so much altered as in the Anura, and therefore the supra- 

 scapula cannot be bent upon the scapula to the same extent as in Frogs and Toads. 

 Here, again, tlie attempt to reconstruct the ancestral bird or birds has to be done in 

 the light of Amphibian Morphology rather than in that of the Eeptilia. The supra- 

 scapular segment in my 1st stage (PI. IX. fig. 1, s.sc.) is most distinct on the right 

 side ; it is one third the length of the scapula (sc), is rounded above, uncinate, and 

 dilated at its base, which enclosed the narrow top of the scapula ; that top is as yet 

 unossified as the suprascapula itself. 



The main scapular segment has the usual gently-bent shape, and is dilated below to 

 form the upper part of the glenoid cavity and the very short acromial process {acp.). 

 The coracoid {cr.) is much wider than the scapula, but it is only three-fifths the length 

 of the whole bar ; its head, which is swollen and large, and its dilated and uncinate 

 base, or epicoracoid region, is as yet unossified ; the rounded and narrow shaft is half 

 the length of the whole bar. Tlie shaft-bone ultimately ossifies the whole of the 

 coracoid in this as in all other birds ; they have, in their adult state, no semi-carti- 

 laginous tract below, such as is seen in Anura and Lacertilia, nor any separate epi- 

 coracoid bone such as we find in the Monotreraes '. 



Seen from above (PI. IX. fig. 2) there is a large uncinate flap of cartilage which 

 grows inwards and hooks downwards upon the upper third of the furcular ramus or 

 clavicle ; this is a continuous precoracoid, and this part, in a very diminished condition, 

 forms the so-called " clavicular process of the coracoid ; " it is the precoracoid of 

 Sabatier (Lindsay, op. cit. p. 715). This part is always present, in the embryo at least, 

 in the Eatitee {op. cit. pi. xvii.^. cr.) ^. 



In the African Ostrich it is as well developed as in the Anura and Cheloiiia {op. cit. 

 pis. v.-vii., xii.-xvii.). One thing more has to be noticed : this large, continuous, pre- 



' In her otherwise very accurate memoir, Miss Lindsay has made a curious mistake with an unlooked-for 

 misstatement of my views. She gives a figure (pL xliv. fig. 1) of the coracoid of Diomedea exulans, and calls 

 the rough top or head of the bone the " coracoid epiphysis " {cor.ep.), and states that this is " Parker's pre- 

 coracoid." It is, at most, au apojiltysis ; birds have very few epiphyses ; generally, the only one is in the 

 " procnemial process " of the tibia. Parker's precoracoid of birds (see ' Shoulder-girdle and Sternum,' pi. xiii. 

 p.cr.) is a special segment or remnant of the fore margin of the great continuous and fenestrated shoulder- 

 plate of a cold-blooded type, a part enucleated in birds from the general precoracoidal bar. 



° ily son. Prof. T. J. Parker, finds it well developed in some embryos of the Apteryx. 

 VOL. XIII. — PART II. No. 4. — Jpiril, 1891. L 



