62 Royal Society. 



length, and the circumference of its distal extremity is 32 inches ! It 

 has a medullary cavity 3 inches in diameter, which at once separates it 

 from the Cetiosaurus and other supposed marine saurians, while its 

 form and proportions distinguish it from the humerus of the Igua- 

 nodon, Hylaeosaurus, and Megalosaurus. It approaches most nearly 

 to the Crocodilians, but possesses characters distinct from any known 

 fossil genus. Its size is stupendous, far surpassing that of the cor- 

 responding bone even of the gigantic Iguanodon ; and the name of 

 Pelorosaurus (from irekwp pelor, monster") is therefore proposed 

 for the genus, with the specific term Conybeari, in honour of the 

 palaeontological labours of the Dean of Llandaff. 



No bones have been found in such contiguity with this humerus, 

 as to render it certain that they belonged to the same gigantic rep- 

 tile ; but several very large caudal vertebrae of peculiar characters, 

 collected from the same quarry, are probably referable to the Pelo- 

 rosaurus; these, together with some distal caudals which belong to 

 the same type, are figured and described by the author. 



Certain femora and other bones from the oolite of Oxfordshire, 

 in the collection of the Dean of Westminster, at Oxford, are men- 

 tioned as possessing characters more allied to those of the Pelo- 

 rosaurus, or to some unknown terrestrial saurian, than to the Ce- 

 tiosaurus, with which they have been confounded. 



As to the magnitude of the animal to which the humerus belonged, 

 Dr. Mantell, while disclaiming the idea of arriving at any certain 

 conclusions from a single bone, states that in a Gavial 18 feet 

 long, the humerus is 1 foot in length; i.e. one-eighteenth part of 

 the length of the animal, from the end of the muzzle to the tip of 

 the tail. According to these admeasurements the Pelorosaurus would 

 be 81 feet long, and its body 20 feet in circumference. But if we 

 assume the length and number of the vertebrae as the scale, we 

 should have a reptile of relatively abbreviated proportions ; even in 

 this case, however, the original creature would far surpass in mag- 

 nitude the most colossal of reptilian forms. 



In conclusion, Dr. Mantell comments on the probable physical 

 conditions of the countries inhabited by the terrestrial reptiles of the 

 secondary ages of geology. These highly-organized colossal land 

 saurians appear to have occupied the same position in those ancient 

 faunas as the large mammalia in those of modern times. The trees 

 and plants whose remains are associated with the fossil bones, mani- 

 fest, by their close affinity to living species, that the islands or con- 

 tinents on which they grew possessed as pure an atmosphere, as 

 high a temperature, and as unclouded skies as those of our tropical 

 climes. There are therefore no legitimate grounds for the hypo- 

 thesis in which some physiologists have indulged, that during the 

 " Age of Reptiles " the earth was in the state of a half-finished 

 planet, and its atmosphere too heavy, from an excess of carbon, for 

 the respiration of warm-blooded animals. Such an opinion can only 

 have originated from a partial view of all the phenomena which 

 these problems embrace, for there is as great a discrepancy between 

 the existing faunas of different regions, as in the extinct groups of 

 animals and plants which geological researches have revealed. 



