1893.] 



OP THE TEEEESTBIAI, VERTEBRATA. 



591 



my own specimen this ligament is superficially calcified, and the 

 acromion is vertically enlarged at its point of origin, in a manner 

 suggestive of a tendency on the part of this bar to fulfil the 

 function of the overgrown epicoracoid of Choice/pus, Brachf2nis, and 

 other genera. In Cholcepus the two conditions coexist. I have 

 loDg desired to work out the detailed anatomy of the Edentate 

 axilla in its bearings on these facts, but the necessary fresh 

 material has not been obtainable. I cannot help thinking, how- 

 ever, that they point to the conclusion that the condition of the 

 coraco-scapular apparatus in Brachj^nis which Mr. Lydekker has 

 descinbed is due to one of a series of adaptive changes which that 

 of the Edentata has undergone in relation to the modification of 

 their fore limb and pronounced peculiarities of life. Certain it 



The blacle-bone of Cydoturvs didacfylus. 2 a, from the ■ 

 side ; 2 h, from the front. X 1|. 



ac. Acromion, co. Coracoid process. Ig. Acromio-scapiilar ligament. 



is, that, except for the joint possession of a bicoracoid, the re- 

 semblances between the Edentate and Dicynodont blade-bones are 

 indicative of nothing but a parallelism of adaptive change; and it 

 is interesting to meet with this in two great gi'oups of animals 

 the ancestors of \\hich we to-day seek independently among the 

 lower Anomodontia. 



I append a list of those Placentalia in which I have observed the 

 metacoracoid, and have much ])leasure in tendering my thanks to 

 Mr. Oldfield Thomas, of tlie Natural History Museum, and to 

 Prof. ('. ytewart and Mr. 11. II. Burne, of the lioyal College of 

 Surgeons, for permission to examine the collections under their 

 charge. 



Edentata. Bradi/jivs cnatUigcr, Mi/nnecojJiar/a, Tamnndua 

 tctraductyla, Tatnsla norenichicta. — Ungulata. Ccrindits reeix'si, 

 E(^uus. — KoDENTiA. Cixloyenys j^taca, Lejms cuniculus, L. timidus, 



