OSTEOLOGY OF CAKNIVOEOUS DINOSAURS. 



63 



slightly concave supero-inferiorly, with a comparatively low obtuse keel, placed 

 more toward the inside of this end. Like the keel on the proximal phalanx of 

 digit 1 it is placed at an angle to the vertical axis of the bone. The concave lateral 

 depressions on either side near the distal extremity are so shallow and illy defined 

 they could hardly be designated as pits. The second phalanx of this digit is slightly 

 longer than the first, with a sharply keeled proximal end and broadly grooved 

 distal aj-ticulating surface. The lateral pits are small but well defined. The ungual 

 phalanx is intermediate in size between those of the first and third toes. 



The proximal phalanx of digit 3 can be distinguished from all others in the foot 

 by the keelless but cupped articular surface of the proximal end (fig. 45, a). It is 

 relatively short, as is the second, the third being more elongate. The proximal 

 ends of the other phalanges of this toe are keeled, and the distal ends are grooved. 

 The ungual, except for its small size, is very similar to the ungual of digit 2. These 

 two unguals are distinguishable from the ungual of digit 1, not only by difference 

 in size, but also by the difference in the direction of the heavy portion below the 

 articulating surfaces. In the two former in the articulated foot it looks almost 

 directly backward, whereas in the first it is. du-ected downward and backward. In 

 all associated fore feet of Theropodous dinosaurs, as shown in the accompanying 

 table, there are two phalanges on the first digit, with a progressive increase to the 

 point where some of the lateral toes have begun to degenerate.- The lengthening 

 of the penultimate phalanges appears peculiar to nearly all Theropodous dinosaurs, 

 and is a mechanical development for the more perfect use of the talons of the fore 

 feet. The principal measurements of the bones of the manus are shown in the 

 following table: 



Measurements of fore-foot elements of Antrodemus valens. 



METACARPALS. 



Greatest length 



Greatest transverse diameter proximal end . 

 Greatest transverse diameter distal end — 

 Least transverse diameter, shaft 



R 



mm. 

 73 

 35 

 36 

 35 





II 



R 



mm.. 



125 



56 



46 



22 



mm. 



122 



63 



46 



22 



III 



R 



mm. 



106 



29 



23 



11 



mm. 

 97 

 28 

 22 

 10 



PHALANGES. 



Greatest length, first row 136 



Greatest length, second row i 118 



Greatest length, third row \ 



Greatest length, fourth row j 



138 

 120 



94 



102 



95 



94 



50 

 41 

 52 

 61 



42 

 43 

 55 

 59 



