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Show 1893.] OF THE TERRESTRIAL VERTEBRATA. 589 exceedingly brief (from two to three weeks in Lepus) ; it arises extends rapidly, and first ankyloses, no less summarily, with either the scapula or epicoracoid. It is therefore a difficult structure to detect, unless we examine a large series of specimens of all ages. In view of these facts, the further study of the Bradypodine girdle can alone show what is the actual share of the coracoid centres in the adult glenoid cavity of that animal; but, be the outcome of this what Pig. 1. The Coracoid Apparatus. la. Lepus, one month after birth; lb. Lepus, 7 weeks, both X l^- tc Sciurus vulgaris, juv. ; Id. Bradypus cuculliger, juv., both X 2. 1 e. Chola>didactylus, half-grown, nat. size. If. Tamandua tetradactyla, front view, adidt, X 1^. 1 g. Tatusia novemcincta, inner aspect, X 1^. 1 h. Ateles marginatus, x 1^. 1 i. Cebus sp., X If- 1 k. Homo, 14-15 years, modified from Sabatier, -J nat. size. ac Acromion. Co'. Epicoracoid. Co". Metacoracoid. Sc. Scapula, ep. Scapular epiphysis, fo. Coraco-scapular foramen. it may, the condition of tbe Cholcepine girdle (as here figured) that the interpretation of Lydekker cannot hold good for the Sloths as a series. In justice "to myself, I am therefore compelled to add that, so far as the point immediately at issue is concerned, the ground traversed by Mr. Lydekker has been already covered in my earlier communication, and I regret that in m y later one, which he cites, I did not add, after the words " most characteristic features," at any rate in its non-reduced form. I have observed the existence of a distinct metacoracoid in the |