I. Researches on the structure, organization, and classification of the fossil reptilia.—Part IX., Section 2. The reputed mammals from the Karroo formation of Cape Colony

Abstract

887, I described some associated bones of an animal from Klipfontein, Fraserberg, r the name Theriodesmus phylarchus (‘Phil. Trans.,' 1888, B., 24). The fossil since received some attention from anatomists, but I am not aware that the place nally assigned to it among the mammalia has been questioned. Professor Carl Bardeleben (‘Proc. Zool. Soc. 1889, p. 259), who critically examined some points y interpretation, concurred that it cannot be said to belong to any known order of mals; and affirms that it is not a reptile in the modern sense of the word. He s that its characters are such that it might be placed between reptiles and imals, but does not offer evidence or argument in support of that determination, is not a substantial difference from my own conclusion, which regarded Theriodesmus as illustrating the reptilian inheritance in the mammalian hand. These lusions may be re-examined in the light of new evidence which I obtained in Africa. Before stating that evidence I propose to examine the interpretation the carpus and phalanges which Professor Bardeleben offers in place of that given paper, published in the 'Philosophical Transactions.’ Professor Bardeleben places four bones in the proximal row of the carpus instead the three bones shown in my restoration. The result of this is to make the carpus than the distal ends of the ulna and radius, so that in his restoration the radius covers a small portion of the smooth proximal articular surface of the bone named me scapho-lunar, and by him named scaphoid. That proximal surface shows no Hence of division into two parts, and, therefore, the hypothetical position assigned it is not supported by evidence. The proposal to name the bone scaphoid is based the hypothesis that I have mistaken the lunar bone for the central bone ; and discovery of this supposed error is the ground for introducing four bones into the proximal row of the carpus. No argument is offered in support of that interpretation and no South African fossil is known with the undisturbed carpus composed in way. In the fossil the carpus is manifestly somewhat displaced, though there is question that the three bones which I have regarded as proximal are substantially their natural positions ; and that the bones of the distal row of the carpus are also their natural positions, in contact with the metacarpal bones, The transverse width over these four distal bones is one-tenth of an inch less than the transverse width over the three bones which I placed in the proximal row. The difference of interpretation is therefore with the bones which I regarded as central bones. These bones a entirely distal in position to the proximal carpal bone, which is in contact with distal end of the radius ; so that, as preserved, the bone which seems to me to be principal central bone is between the magnum and the outer side of the bone articulates with the radius; and that central bone which Professor Bardeleben idenfies as the lunar bone, is in close lateral contact on its inner side with the bones whit he regards as central. There is, I submit, no evidence for the suggested transposith of the bone from the middle row of the carpus to the proximal row; and no arguinet is offered in support of the change of interpretation. The distal end of the rads gives no indication of having supported two bones; while on the outer distal surface of the scapho-lunar is a distinct facet which seems to correspond in size and position with the central bone which is below it.