Prof. Huxley on the Animals between Birds and Reptiles. 73 



metatarsal of the hallux is much smaller at its proximal than at its 

 distal end. 



Iguanodon has three large toes, of which the middle is the longest. 

 The slender proximal end of a first metatarsal has been found adhe- 

 rent to the inner face of the second ; so that if the hallux was com- 

 pletely developed, it was probably very small. No rudiment of the 

 outer toe has been observed. 



It is clear, from the manner in which the three principal meta- 

 tarsals articulate together, that they were very intimately and firmly 

 united, and that a sufficient base for the support of the body was 

 afforded by the spreading out of the phalangeal regions of the toes. 



From the great difference in size between the fore and hind limbs, 

 Mantell, and more recently Leidy, have concluded that the Dino- 

 sauria (at least Iguanodon and Hadrosaurus) may have supported 

 themselves for a longer or shorter period upon their hind legs. But 

 the discoveiy made in the weald, by Mr. Beckles, of pairs of large 

 three-toed footprints, of such a size and at such a distance apart 

 that it is difficult to believe they can have been made by anything 

 but an Iguanodon, lead to the supposition that this vast reptile, and 

 perhaps others of its family, must have walked, temporarily or per- 

 manently, upon its hind legs. 



However this may be, there can be no doubt that the hind quarters 

 of the D'mosauria wonderfully approached those of birds in their gene- 

 ral structure, and therefore that these extinct reptiles were more 

 closely allied to birds than any which now live. 



But a single specimen, obtained from those Solenhofen slates to 

 the accident of whose existence and usefulness in the arts palseonto- 

 logy is so much indebted, affords a still nearer approximation to the 

 *' missing link " between reptiles and birds. This is the singular 

 reptile which has been described and named Compsognaihus longijpes 

 by the late Andreas Wagner, and some of the more recondite orni- 

 thic affinities of which have been since pointed out by Gegenbaur. 

 !N'otwithstanding its small size (it was not much more than 2 feet in 

 length), this reptile must, I think, be placed among, or close to, the 

 D'mosauria ; but it is still more bird-like than any of the animals 

 which are ordinarily included in that group. 



Compsognaihus longipes has a light head, with toothed jaws, sup- 

 ported upon a very long and slender neck. The ilia are prolonged 

 in front of and behind the acetabulum. The pubes seem to have 

 been remarkably long and slender (a circumstance which rather 

 favours the interpretation of the so-called " clavicles " of Iguanodon 

 as pubes). The fore limb is very small. The bones of the manus 

 are unfortunately shattered ; but only four claws are to be found, so 

 that possibly each manus may have had but two clawed digits. 



The hind limb is very large, and disposed as in birds. As in the 

 latter class, the femur is shorter than the tibia — a circumstance in 

 which Compsognaihus is more ornithic than the ordinary Binosauria. 



The proximal division of the tarsus is ankylosed with the tibia, as 

 in birds. In the foot the distal tarsals are not united with the three 



