398 B. M. S. Watson — The Cheirotherium. 



outward and backward. The first and second toes often show traces 

 of distinct pads, there being two on the first and three on the second 

 digit. It is obvious, from inspection of good prints, that these pads 

 lie below the articulations, as in Dr. Lull's Dinosaurs, and not 

 between them as in ourselves. The distal end of each digit ends 

 in a small claw, which extends beyond the pad. The posterior ends 

 of the pads of the toes are separated when lightly impressed and 

 represent the articulation between the lower ends of the metatarsals 

 and the first phalanges. 



The sudden termination of the pads behind shows that the 

 metacarpus was carried clear of the ground, i.e. that the animal 

 was digitigrade. In some exceptional specimens the pads run into 

 a distinct sole, as is, for example, the case in the type-specimen of 

 Cheirotherium hercuUs; in such cases, which, may represent a resting 

 position, the 'heel', which is presumably made by the metacarpus, 

 is slightly longer than the phalangeal part of the impression. The 



Fig. 2. — Eestoration of Plateosaurus from specimens in the Berlin 

 Museum. After an outline figure by Professor Jaekel, in Die 

 Woche, Hft. xxvi, Berlin, 1912. ^ 



fifth digit, which we have not hitherto considered, lies in an 

 extremely curious position with its very large posterior pad behind 

 the third digit. The whole arrangement suggests that the metatarsal 

 acted as a sort of strut to the tarsus, the other four metatarsals 

 standing not quite vertically, but at some angle between that and 

 horizontally. It is, unfortunately, impossible to determine the 

 number of phalanges in this toe, but it is not improbable that there 

 were only two. No known Triassic Dinosaur has so well-developed 

 a fifth toe as Cheirotherium, but the foot of Plateosaurus seems to me 

 not very dissimilar, and it is quite possibly a descendant of that 

 animal. The further reduction of the fifth digit in most Dinosaurs 

 may conceivably be due to the fact that when the metatarsus became 

 vertical its use as a strut disappeared, and, as no other use for it 

 presented itself, it was rapidly aborted. 



^ [This Text-figure, from the Guide to Friar Park, Henley-on-Thames (1914), 

 p. 27, fig. 12, was kindly lent by Sir Frank Crisp, Bart. (The scales have been 

 added, and are not in Professor Jaekel's outline figure.) — Ed. Geol. Mag.] 



