ON BRITISH FOSSIL REPTILES. 109 



Sclncus. It is slightly arcuated longitudinally, subtrihedral in the middle, flat- 

 tened and expanded at the two extremities. If it be really a clavicle, it forms 

 as characteristic an indication of the Lacertian affinities of the Megalosaurus 

 as the coracoid. According to the proportions of the clavicle in existing lizards, 

 Cuvier observes that it bespeaks an animal nearly sixty feet in length. 



A subcompressed, three-sided bone, flattened and slightly expanded at one 

 end, thickened and more suddenly extended transversely at the opposite end, 

 which formed part of a large cotyloid cavity, is most likely an ischium ; its 

 length is 18 inches; its breadth, at the middle of the shaft, 5 inches ; at its 

 articular end 9 inches, the thickness of this end being 4 inches. The ascend- 

 ing shaft of this bone is slightly twisted, convex and smooth on the outer side, 

 flat and rough on the inner side. 



Other bones, not improbably belonging to the Megalosaurus, are preserved 

 in the British and Oxford Museums, and in the private collections of Messrs. 

 Holmes and Saull ; but further evidence of their Megalosaurian character 

 must be obtained before a description of them can be profitably applied to the 

 reconstruction of the skeleton of the present carnivorous Dinosaur, 



A few words, however, may be added, touching the size of the Megalosau- 

 rus ; for it appears to me that the calculations which assign to it a length of 

 60 and 70 feet are affected by the fallacy of concluding that the locomotive 

 extremities bore the same proportion to, and share in the support of, the body, 

 as they do in the small modern land lizards. 



The most probable approximation to a true notion of the actual length of 

 the Megalosaurus, is that which may be obtained by taking the length of the 

 vertebrge as the basis. The antero-posterior dimension is the most constant 

 which the vertebrae present throughout the spine : in most Crocodilian and 

 Lacertian reptiles the cervical vertebrae are a little shorter than tlie dorsal ; 

 but these are of equal length, and the caudal vertebrae maintain the same 

 length to very near the extremity of the tail. 



As the dorsal vertebree of the Megalosaurus agree, in the important cha- 

 racter of the mode of articulation of the ribs, with the Crocodiles, it may be 

 regarded as most probable that they also corresponded in their number. This 

 does not exceed 14 in recent Crocodiles, nor 16 in any of the known extinct 

 species ; taking, then, the latter number, and adding to it 7, the usual number 

 of the cervical vertebrae in Crocodiles, we may allow the Megalosaurus 23 

 vertebrte of the trunk. 



The length of the body of a large dorsal vertebra of the Megalosaurus in 

 the British Museum is 41 inches : from the analogy of the Iguanodon, in 

 which several dorsal vertebrae have been discovered in their natural juxta- 

 position, it is probable that the thickness of the intervertebral substance did 

 not exceed one-third of an inch : but if we multiply 23 by 5, not allowing 

 for the probable shortness of the cervical vertebrte, we only then attain a 

 length of 9 feet 7 inches. If, however, setting aside the analogy of the Me- 

 galosaurus to the Crocodiles in the structure of the vertebrte, we take that 

 species of Lacertian which it most resembles in the structure of the teeth, and 

 found our calculation on the number of vertebrae of the trunk in such lizard, 

 then, the great carnivorous Varanian Monitor of Java having 27 vertebrte 

 of the trunk, we do not, even calculating the same number of vertebraj to 

 have occupied each a space of five inches in the Megalosaurus, obtain a length 

 of trunk exceeding 11 feet 3 inches. 



I should consider the first calculation, or about 10 feet, to have been the 

 most probable natural length. 



To this we must add 1 foot 10 inches for the known length of the sacrum. 

 Thus 12 feet will be a fair or even a liberal allowance of length from the 



