1893.] Oy THE CORACOID OF THE TERRESTRIAL VERTEBRATA. 585 



7. On the Coracoid of the Terrestrial Vertebrata. By G. B. 

 Howes, F.Z.S., F.L.S., Assistant Professor of Zoology, 

 Roy. Coll. Sci. Lond. 



[Eeceived June 20, 1893.] 



I. As to Teryninologij. 



It is now generally conceded that some of the Anomodout 

 reptiles, which in many respects so closely approximate towards 

 the jMammalia in their skeletal anatomy, were possessed of an 

 expanded epicoracoid of the Monotreme type. Professor Seelev, 

 to whom we are chiefly indebted for the discoveries which ha\e 

 rendered this conclusion clear, discards the Cuvierian term " epi- 

 coracoid" and persistently applies the term precoracoid to the 

 element in question in both reptiles and mammals '. 



In this he is followed by Mr. Hulke '^. Mr. Lydekker, however, 

 in a recent communication to this Society ^, has proposed to abolish 

 the term epicoracoid altogether, in association with a discovery of my 

 OMn^ that the element to which in the Monotreme the term 'epi- 

 coracoid ' was first applied is the serial homologue of the coracoid 

 process of the higher mammals, to which, in the long run, the 

 term ' coracoid ' was originally given. 



The terra precoracoid (procoracoid of Gregenbaur) is well known 

 to be used in two or more totally distinct senses (sometimes by the 

 same observer in the same paper '). It is for the most part either 

 applied to a mere process of the coracoid, most variable in its 

 relationships when present and in no sense originally distinct, 

 or restricted to that bar which underhes the clavicle * and (some 



' Cf. Phil. Trans. 1888, B. pp. 490-492, 1889, B. pp. 255 and 275, and 

 P. R. S. vol. li. p. ] 19. 



= P. R. S. vol. li. p. 233. 



3 See P. Z. S. 1893, p. 172. 



* Journ. Anat. & Phys. vol xsi. p. 192. 



' Cf. Hulke, loc. cit. description of figs. 4, 6, 7, and 9. 



^ Goette, as is well known, confirmed Eathke's discovery of this '" Anlage " in 

 the young liaird. The contradictory arguments which have been based upon 

 its supposed distinctness or non-distinctness in this or that animal lose their 

 force to-day in the tendency of recent research to demonstrate, more and more 

 clearly, that the three great elements of both the pectoral and pelvic girdles 

 are at first independently differentiated. {Cf. especially the papers of Miss 

 Lindsay in P. Z. S. 188.J, p. (592, and of Mehnert in Morph. Jahrb. Bd. xiii. 

 p. 293, &Bd. XV. p. 110). 



There can, I think, belittle doubt that the Rathke-Parker conclusion that the 

 dermo-clavicular elements are in the Chelonia represented by the ecto-and ento- 

 plastra is correct. It appears to me highly probable that in these animals the 

 claviculo-coracoid apparatus has undergone a kind of analj'sis into its consti- 

 tuent elements, and tliat the precoracoid (in the non-differentiation of a distinct 

 endosteal centre within its substance, such as Gegenbaur first described for 

 man himself) has become ossified by an extension of the acromial tract. Baur 

 has lately proposed to term this apparent acromion a ' proscapula ' (c/. Proc. 

 Acad. Nat. Sci. Philad. 1891, p. 424), a by no means inappropriate term, if a 

 new one be necessarv. 



