Reviews — Cretaceous Dinosaur Gorgosaurus. 519 



fossils and with drawings of all the described specimens which have 

 not hitherto been figured. It is a most valuable work of reference 

 and indispensable for further progress. It is now possible to 

 understand how fragmentary is our knowledge of the various genera 

 and species, and how much scope there is for differences of opinion 

 on all points except generalities. The broad outlines of equine 

 evolution are clearer than ever, and Professor Osborn has had 

 prepared new series of beautiful drawings to illustrate the changes 

 in the upper and lower molar teeth and in the feet. The excellent 

 manner in which the stratigraphical position of the various fossils is 

 determined is also fundamentally important. We are only inclined 

 to ask for more, and would add to our congratulations our best 

 wishes for the speedy accomplishment of Professor Osborn's promised 

 Monograph of the Equidae. 



V. — The Cretaceous Theropodous Dinosaur Gorgosaubus. By 

 Lawrence L. Lambe. Canada Dept. of Mines, Memoir 100, 

 Geological Series, Ottawa, 1917. 



IN this excellently illustrated memoir the author gives a full 

 account of a nearly complete skeleton of a large carnivorous 

 Dinosaur, Gorgosaurus lihratus, found in the Belly River (Cretaceous) 

 beds of Alberta, Canada. This reptile is, in most respects, very^ 

 similar to Tyrmmosaurus, but is said to differ from it in several 

 important particulars, e.g. in the structure of some of the teeth, the 

 proportions of the limbs, and the great development of the plastron 

 of ventral ribs. The fore-limb is curiously small, less than one- 

 fourth the length of the hind-limb. It possesses only two complete 

 digits (1 and 2), with powerful claws, and a vestige of the third 

 metacarpal; the radius and ulna are very short. The hind-limb is 

 remarkable for the great elongation of the foot, which, though much 

 larger, is very similar to that of Ornithomitnus . It possesses three 

 complete digits (2, 3, 4) and the distal portion of the first, all claw- 

 bearing. The fifth is represented by a vestige of the metatarsal 

 only. The ventral buckler is very well developed, and consists of 

 about nineteen transverse rows of ventral ribs, two pairs in each 

 row. In the first and last the median pieces are fused, but in the 

 others they remain distinct but overlap, and are firmly attached to 

 one another, there being no median more or less V-shaped element 

 such as usually occurs in reptiles with such a plastron. The author 

 discusses the probable appearance and habits of this reptile, giving 

 several restorations of it in what he believes to be characteristic 

 attitudes. He considers that, although its mode of progression was 

 bipedal, in a semi-erect position, and well raised from the ground, 

 that when at rest the animal squatted, supported on the expanded 

 ends of the pubes, or lay extended on its ventml surface. The 

 absence of wear on the teeth suggests that the food was soft and 

 obtainable without much effort, probably consisting mainly of the 

 flesh of carcases of other reptiles such as the large Trachodont 

 Dinosaurs. 



C. W. A. 



