326 Reports & Proceedings — Geological Society of London. 



Upper Carboniferous times tlie line probably passed through some 

 primitive generalized Pelycosaurs ; in Lower Permian through primi- 

 tive, probably Therocephalian, Therapsids. In Middle and Upper 

 Permian the line passed through the Gorgonopsia. In Triassie times 

 the mammalian ancestors were small generalized Cynodonts. In 

 Lower Jurassic the mammals are so Cynodont-like, and the Cynodonts 

 so mammal-like, that in no single case are we absolutely certain 

 which is which. 



In the Therocephalia, the Gorgonopsia, and the Cynodontia, the 

 skull is very mammal-like. The zygomatic arch is, as in mammals, 

 formed by the jugal and the squamosal. The teeth are divided into 

 incisors, canines, and molars. In the later Gorgonopsians there is 

 an imperfect secondary palate ; in Cynodonts a complete secondary 

 palate as in mammals. In Permian Therapsids there is a single 

 occipital condyle ; in the Triassie Cynodonts there may be a single 

 condyle slightly divided or two exoccipital condyles. There is, on 

 passing from earlier to later types, a steady increase in the size of 

 the dentary and decrease in the size of the other elements of the jaw. 

 The quadrate also becomes much reduced in the higher types. In 

 Gorgonopsians and probably all earlier types the arch of the atlas is 

 a pair of bones; in Cynodonts, as in mammals, there is a single arch. 



It is argued that the small Gorgonopsians fed almost exclusively 

 on the comparatively slow-moving, small, herbivorous Anomodonts. 

 In the Trias the small Anomodonts became very rare, and the 

 carnivorous Therapsids had to feed on other small forms, apparently 

 the more active lizard-like Cotylosaurs, such as Procolophon. The 

 change of habit resulted in the Cynodontia. 



In Upper Triassie times the larger Cynodonts preyed upon the 

 large Anomodont, Kannemeyeria, and carried on their existence so 

 long as these Anomodonts survived, but died out with them about 

 the end of the Trias or in Ilhsetic times. The small Cynodonts, 

 having neither small Anomodonts nor small Cotylosaurs to feed on, 

 were forced to hunt the very active long-limbed Thecodonts. The 

 greatly increased activity brought about that series of changes which 

 formed the mammals — the flexible skin with hair, the four-chambered 

 heart and warm blood, the loose jaw with teeth for mastication, an 

 increased development of tactile sensation, and a great increase of 

 cerebrum. Not improbably the attacks of the newly evolved Cynodont 

 or mammalian type brought about a corresponding evolution in the 

 Pseudosuchian Thecodonts which ultimately resulted in the formation 

 of Dinosaurs and Birds. 



II. — Geological Society of London. 



(i) May 28, 1913.— Dr. Aubrey Strahan, E.E.S., President, 

 in the Chair. 

 The President, in referring to the loss which the Society had that 

 day sustained by the decease of John Lubbock, 1st Baron Avebury, 

 recalled the fact that Lord Avebury had been a Fellow of the Society 

 for no less than fifty-eight years, that he had contributed several 

 valuable papers to the Society's Journal, and that he was the recipient 



