resemblance to the mammalian skull; in fact it explains the origin of two condyles from the typical reptilian single condyle, and disposes of the necessity for believing, with Huxley and others, the Amphibia to be on the main line of mammalian evolution on account of their two condyles. The general aspect of the skull in _Cynognathus_ has been {94} compared to that "of _Thylacinus_ or _Dissacus_." No one can examine the actual sketches of the skull of that Theriodont without endorsing that opinion. As a curious detailed point of likeness to certain Mammalia may be mentioned "a small descending process of the malar bone, which may be a diminutive representative of the descending element of the malar seen in _Elotherium_, _Nototherium_, _Diprotodon_, _Macropus_, certain Edentata, such as _Glyptodon_, _Megatherium_, _Mylodon_, _Bradypus_, but unparalleled so far as I am aware in fossil reptiles." (Osborn.) The zoologist cannot help being impressed with the significance of small details of similarity, which do not seem to be due in any way to surrounding conditions of life, and thus referable to mere convergence, like the fish-like form of Whales and Seals. The rest of the skeleton of the Theriodontia is by no means so well known as the skull and teeth. But from what is known, other mammalian characters can be pointed out. Perhaps the most striking mammalian feature is to be found in the scapula of _Cynognathus_. It is in this creature somewhat narrow and elongated; but it has a well-marked spine, ending in a hooked acromion. Now it is to be noted in support, so far, of the diphyletic origin of mammals, that in the Monotreme, as in Whales indeed, the spine forms the anterior border of the scapula, and is coincident with it, there being thus no prescapula at all in the Monotreme, and only a trace of it in certain Whales.[47] Whether the multituberculate _Tritylodon_ or _Diademodon_ had a scapula after the Monotreme pattern is not known; but it is clear that the scapula of the triconodont _Cynognathus_ is quite after the pattern of the Eutherian scapula. Furthermore, Professor Seeley is of opinion that the coracoid was relatively small, and indeed smaller than the same bone in Edentates, and _a fortiori_ than in Monotremes. Another fact of structure which points also, possibly, in the direction of a diphyletic origin for the Mammalia, is the double-headed ribs of _Cynognathus_. As is well known, the ribs of the Monotremata have only the central head, the capitulum.