1893.] 



OF THE TEBRESTRIAL TBETEBBATA. 



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 epieoracoid of Cholospus, Bradypus, and 

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

 long 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 Brcuhipus which Mr. Lydekker has 

 described 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 



Kg. 2. 



ac. 



The blade-bone of Cycloturus didactylus. 2 a, from the 

 side ; 2 b, from the front. X 1^. 



ac. Acromion, co. Coracoid process. Ig. Acromio-scapular 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 groups of animals 

 the ancestors of which we to-day seek independently among the 

 lower Anomodontia. 



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

 metacoracoid, and have much pleasure in tendering my thanks to 

 Mr. Oldtield Thomas, of the Natural History Museum, and to 

 Prof. C. Stewart and Mr. E. H. Burne, of the Eoyal College of 

 Surgeons, for permission to examine the collections under their 

 charge. 



Edentata. Bradypus cucidlic/er, Myrmecophaga, Tamandua 

 tetradactyla, Tatusia novemcincta. — Ungulata. Cervulus reevesi, 

 Equus. — EoDENTlA. Coeloffenys paca, Lepus ciiniculus, L, timidus, 



