RECORDS OF MEETINGS 305 



We find many other mammal-like reptiles of which the Therocepha- 

 lians, Dromasaurians and the Cynodonts are the most important. Al- 

 though these insectivorous and carnivorous types are less mammal-like 

 in some respects than the Anomodonts, they agree more closely with the 

 mammals in the construction of the skull. They all have long, slender 

 limbs adapted for running. The earlier members, such as the lower 

 Therocephalians, have the number of toe joints as still found in the liz- 

 ards and most reptiles, viz., 2, 3, 4, 5, 3 ; but the Anomodonts, the lower 

 Dromasaurians and the higher Cynodonts have the same number of joints 

 in the toes as is retained in ourselves, 2, 3, 3, 3, 3. It is rather interest- 

 ing to look at one^s hand and realize that the fingers have all these joints 

 because a remote ancestor took to walking with the feet under the body, 

 supporting it off the ground, rather than with the feet to the side as in 

 the lizards and crocodiles. 



The Cynodonts occur in the Triassic formation and a few survive into 

 the Jurassic. In most points of structure, they are extremely mammal- 

 like and it is frequently impossible, if the specimen is at all incomplete, 

 to say whether we are dealing with one of the Cynodonts or a mammal. 

 The lower jaw is almost entirely formed by a large single bone, the pos- 

 terior bones being small, and the bone on which the jaw hinges is also 

 small, thus foreshadowing the mammalian condition, the dentary bone, 

 the angular, articular and surangular being quite small, as is also the 

 quadrate bone. The teeth are in most forms of a carnivorous type, com- 

 posed of sharp incisors, long sharp canines and cusped molars, the cusps 

 being almost exactly like those of the carnivorous mammals. 



A couple of months ago, I discovered that in the Cynodonts, the in- 

 cisors, canines and premolars are preceded by an earlier set exactly as 

 in ourselves. It would probably be inappropriate to call them milk teeth, 

 as it is very unlikely that the Cynodonts provided their young with milk, 

 but there can be no doubt that the young had a first temporary set of 

 front teeth like most mammals. 



Besides solving the question of the origin of the mammals, the Karroo 

 fossil beds have thrown some light on the origin of birds. There has been 

 •considerable discussion as to whether birds were derived from flying bat- 

 like reptiles called pterodactyls or from the dinosaurs. Some have even 

 gone so far as to derive the flying birds from the pterodactyls and the 

 running birds such as the ostrich from the dinosaurs. Dr. Lucas is one 

 of those who favors a double origin for the birds. Professor Osborn some 

 years ago argued in favor of the birds and dinosaurs having come from a 

 common ancestor in Permian times. A few years ago I maintained, as 

 the result of my studies on the development of the ostrich, that the an- 



