1893.] OP THE TEREESTEIAL VEETEBRATA. 5S7 



portion of the coracoidal skeleton not involved in the clavicular 

 apparatus, and to its homologue the term coracoid is applied in all 

 the ]o\^"er Yertebrata, whether it be ossified or not. What, then, 

 are we to term this, if Mr. Lydekker's system is to endure ? The 

 context of his paper suggests coracoido-metacoracoid as a likely 

 term ; but before that could be introduced it ought to be shown 

 that the single ' coracoid ' of living Lizards, which is coincident 

 in area with the conjoint coracoidal elements of Anomodonts and 

 Mammals, is the product of fusion of these. No one has yet 

 demonstrated the remotest trace of more than a single centre of 

 ossification in the Lacertilian coracoid ; while, on the other hand, 

 its double ossification in the Mammalia, in its non-abbreviated 

 form (Ornithorhi/nchus), is preceded by its segmentation while still 

 cartilaginous. Mr. Lydekker's proposals might perhaps be accepted 

 were the Mammalia aud Anomodoutia alone concerned. Anatomical 

 terminology, however, unlike nomenclature in systematics, must 

 needs be applicable to all classes of this or that sub-kingdom ; and 

 it has therefore to cover a very \Wde range of structural variation. 

 These considerations, together with those wliich I have already 

 raised, appear to me fatal to the acceptation of Mr. Lydekker's 

 terms, which seem no more tenable than the appUcation of the 

 human anatomists' term 'scapula' to the coraco-scapular 'blade- 

 bone,' into which he lapses in his final footnote on p. 174, and 

 wldch, on grounds of sheer priority, should be adhered to. We are 

 dealing Mith a common (coracoidal) cartilage, which is in some 

 animals replaced by a couple of osseous elements, and in others 

 by but one. Setting aside the precoracoid aud clavicle, the 

 ultimate homologies of which are by no means yet fully worked 

 out, our present requirements may be met by the retention of the 

 universal term coracoid for the entire set of structures (i.e. the 

 cartilaginous 'coracoid' bar audits derivatives), with the introduc- 

 tion of, say, the terms uincoracoldal and hicoracoidal for its diversely 

 modified tvpes, and the retention of Cuvier's ejncoracoid for its 

 anterior and Lydekker's metacoracoid for its posterior segment in 

 the latter one. L^pon this basis, the sum of our knowledge of the 

 coracoid of Amphibia and Amniotamay be formulated as follows : — 



Coracoid. 



i. uaicoracoidal. Amphibia, all living Reptilia, Aves. 

 ii. hicoracoidal. tSome Anomodoutia, Mammalia, Ich- 

 thyosauria aud Nothosauria (?). 



A simple alternative would be the description of the common 

 coracoid as either uni- or bi-segmented ; but this, for obvJDUS 

 reasons, would be insufficient. The arrangement which I here 

 propose admits of the retention of the human anatomisls' term 

 'coracoid process' as all-siiillcient for the requirements of the 

 systematic niammalogist, who, except for hia concern with the 

 JMonotreiiies, deals with tlie vexed element only in its must abbre- 

 viated and vestigial conditions. 



