NO. 1GC6. OSTEOLOGY OF CAMPTOSAURlSl-~aiLMOR£!. 265 



external border a thin lip-like process is developed which laps over 

 and is closely applied to a roughened surface on the antero-internal 

 border of the shaft of Metatarsal III. At this point the shaft is 

 bent outward, which throws the distal part aw^ay from the median 

 bone. The distal end is stout, and subquadrilateral in outline, ex- 

 cei3t that it is bisected by a deep, rounded notch on the posterior 

 border. This end is rounded antero-posteriorly. The pits for the 

 attachment of lateral ligaments are large and fairly deep. The 

 proximal end of the third metatarsal is roughly triangular in outline, 

 the thickened portion being in front. The articular surface is 

 roughened and slightly concave for the reception of the flattened 

 tarsale of the distal row. The inner surface of the proximal half 

 is plane, but below, this border of the shaft is rounded. Viewed 

 anteriorly the bone remains about the same wndth, being slightly ex- 

 panded at the distal end. Viewed laterally, however, the shaft con- 

 tracts rapidly from the proximal toward the distal pulley-like articu- 

 lar end. The external surface of the proximal end has two oblique 

 faces, which are opposed by the excavated internal surface of the 

 fourth metatarsal. The pits for the attachment of lateral ligaments 

 are large but shallow. 



Seen from the proximal end the fourth metatarsal is subtriangular, 

 the apex being directed outward. The slightly roughened articular 

 surface in front is concave and receives the distal tarsale closely. 

 The internal surface of the upper half is roughened and fits closely 

 to the upper surface of the third metatarsal. The shaft is com- 

 pressed antero-posteriorly and is wider than thick. As in the second 

 metatarsal the lower half diverges outwardly and is free from the 

 median or third metatarsal. The distal end is expanded, more espe- 

 cially antero-posteriorly than laterally. The distal articular end is 

 rounded and roughened on the posterior but smooth on the anterior 

 half. The pits for the lateral ligaments are large, the internal being 

 shallow, the external very deep. The numbers of the phalanges, 

 beginning with the first, are 2, 3, 4, 5, and correspond, as Hulke " has 

 pointed out, to the first, second, third, and fourth toes in the foot of 

 existing lizards and birds. Ilypsilophodon foxii has the same for- 

 mula. The proximal phalanges are rather long, with pulley-shaped 

 distal and concave proximal ends. The phalanges have their articu- 

 lating ends closely applied to one another. A median rounded verti- 

 cal ridge on the proximal end fits into a corresponding depression 

 on the proximal end of another, thus forming a strong union which 

 would allow but little lateral motion. There are deep, well-defined 

 lateral pits for the attachment of ligaments on most of the phalanges. 

 The second, third, and fourth phalanges of Digit IV are considerably 

 more shortened than the other phalanges. The ungual phalanges 



« Phil. Trans. Roy. Soc. London, CLXXIII, 1882, p. 1053. 



