572 Geological Society of London. 



II. Ichthyornis dispar (Marsh), discovered by Prof. O. C. Marsh in 1872 in the 

 Upper Creataceous beds of Kansas, U.S. It possessed well-developed teeth in 

 both jaws. The teeth are set in distinct sockets, and are more or less inclined 

 backwards. 



III. Odontopteryx toliapica (Owen), an Eocene bird from the London Clay of 

 Sheppey, the skull of which alone has been discovered, has very prominent den- 

 ticulations of the alveolar margins of the jaws. 



The author then referred to the Dinosauria, some of which he considered to 

 present points of structure tending towards the so-called wingless birds. 



I. Compsognaihus longipes (K. Wagner), from the Oolite of Solenhofen, is about 

 two feet in length, having a small head with toothed jaws, supported on a long and 

 slender neck. 



The iliac bones are prolonged in front of and behind the acetabulum ; the pubes 

 are long and slender. The bones of the fore limbs are small, and were probably 

 furnished with two clawed digits. The hind limb is very large, and disposed as 

 in birds, the femur being shorter than the tibia. The proximal division of the 

 tarsus is anchylosed with the tibia as in birds. 



II. The huge carnivorous Megalosaw'us, ranging from the Lias to the Wealden, 

 had strong but not massive hind limbs, and short reduced fore limbs ; it moved 

 with free steps, chiefly if not solely on its hind limbs, which is true also of the 

 vegetable-feeding lizards of the Mesozoic rocks. 



The author next drew attention to the Frilled Lizard of Australia {Chla^nydo- 

 saurus Kingii, Gray), which has its fore limbs very much smaller than the hind 

 limbs, and has been observed not only to sit up occasionally, but to run habitually 

 upon the ground on its hind legs, its fore paws not touching the earth, which 

 upright carriage necessitates special modifications of the sacrum and pelvic bones. 



The Solenhofen Limestone, in which Pterosauria are frequent, and which has 

 yielded the remains of Arc/iceopte^yx and of Conipsognathus, has also furnished a 

 'slab bearing a bipedal track, resembling what might be produced by Chlamydo- 

 saurtis or Compsognathus. It shows a median track formed by the tail in being 

 drawn along the ground ; on each side of this the hind feet with outspread toes 

 leave their mark, while the fore feet just touch the ground, leaving dot-like im- 

 pressions nearer the median line. Hence the author thought that while some of 

 the bipedal tracks which are met with from the Trias upwards may be the "spoor" 

 of Struthious birds, most of them are due to the bipedal progression of the Secondary 

 Reptiles. 



Discussion. — Mr. Seeley thought that the footprints on the slab cited in the 

 paper had been produced by some saurian, such as a Pterodactyle, the fore limbs 

 of which were wider apart than its hind limbs, rather than by Compsognathus. If 

 the foot-track had been due to a saurian walking on its hind legs only, he thought 

 that the principal impressions must of necessity have been nearer together. He 

 disputed the correctness of the term "adaptive modification" as applied to the air- 

 cavities in bones. He was inclined to regard the Pterodactyle as more closely 

 allied to Birds than did the author of the paper. The condition of the carpus, as 

 well as the tarsus, in these reptiles showed their ornithic affinities. He cited 

 jerboas, kangaroos, and other forms, in which the hind legs were mainly used 

 for progression, but in which the sacrum and other bones were not modified, as 

 instances calculated to inspire caution in connecting the mode of progression with 

 structure. 



Mr. Hulke could not regard the tracks as those of a Pterodactyle, as the inner 

 marks were much less distinct than the outer, and would therefore hardly be due 

 to the hinder limbs, on which the weight would mainly, fall. 



Mr. Blanford agreed with Mr. Seeley that the mere fact of the Chlamydosaurus 

 walking on its hind legs did not suffice to prove any affinity with Dinosaurians. 



Mr. Woodward, in reply, stated that the two points on which he had mainly 

 founded the paper were : — ist, the occurrence of footprints in the Solenhofen lime- 

 stone, characteristic of a bipedal progression of some saurian, which had, moreover, 

 used its tail from time to time to give it a forward impetus ; and andly, the method 

 of walking of Chlamydosaurus. With regard to animals thus progressing, he was 

 not prepared to accept the view that there was no corresponding modification in 

 structure. 



3. "Note on the hs\xz.g?iXvi% oi Iguanodon Mantelli." By J. W. Hulke, Esq., 

 F.R.S., F.G.S. 



