NO. 1666. OSTEOLOGY OP CAMPT08AURUS—GILMORE. 255 



The internal side is longer than the external. The proximal articular 

 end is concave supero-inferiorly, with a blunt median keel for articu- 

 lation Avith the groove on the distal articular surface of Metacarpal I. 

 The distal end is regularly convex supero-inferiorly and concave 

 transversely. This description is based on the phalanx of the left 

 forefoot of C. hroioni. The ungual of Digit T is missing on all of 

 the feet studied, but in the specimen shown in fig. 29 this element 

 has been provisionally restored. 



The proximal phalanges of Digits II and III are short, stout, 

 block-like bones. The proximal articular ends are concave supero- 

 inferiorly, with a median concave depression. The second phalanges 

 of the above digits are much shortened, with concave proximal and 

 convex distal ends. The palmar surfaces are flattened and produced 

 posteriorly into thin sheets which lie under the distal ends of the 

 proximal phalanges of their respective digits. This posterior exten- 

 sion is especially pronounced in the second phalanx of Digit IV. 



Digits II and III are terminated by relatively large, pointed un- 

 guals, which were undoubtedly sheathed in horny claws, as indicated 

 by a pair of lateral grooves on each ungual. The ungual of Digit II 

 is considerably depressed; the proximal end is subtriangular in out- 

 line with concave supero-inferior surface. The median dorsal sur- 

 face is produced posteriorly and overhangs somewhat this articular 

 end. The proximal end of this ungual of Digit III is higher than 

 wide and in outline is irregularly rounded. The articular end is more 

 deeply concave than ungual two. The anterior end is deflected 

 toward the foot of the opposite side and is sharply pointed. The 

 proximal phalanx of the fourth digit is much depressed, especially at 

 the distal end. and expanded transversely at the proximal end. The 

 articular surface of this end is concave supero-inferiorly with only 

 a faint indication of a keel on the superior part of the median sur- 

 face. The palmar surface is flattened. The transverse extent of the 

 distal end is much less than the proximal. It is convex supero-in- 

 feriorly with a suggestion of a concave median groove. The second 

 phalanx of this digit is very short and supports a small, rounded, 

 hemispherical, terminal phalanx which in life was probably embedded 

 within the integument of the foot. The proximal end of the latter 

 is indicated by a concave surface. 



The proximal phalanx of Digit V is the most slender of the series. 

 The upper articular end is about evenly concave in both transverse 

 and vertical directions and tapers Avithout noticeable constriction 

 to the distal end, which is convex supero-inferiorly. The terminal 

 phalanx of this digit is an irregular button-like ossicle. 



From the above description and figures of the manus of Campto- 

 saurus it will be seen that the weight of the body was borne prin- 

 cipally on the three median digits, and that through disuse the fifth 



