DR. MANTELL ON THE PELOROSAURUS. 
387 
islands that has reached this country ; and I could but think, that had the respective 
localities and periods of these birds and reptiles, — both of a size far surpassing all 
other known types of their respective classes, — been interchanged, and the bones of 
the Dinornis of New Zealand referred to the Wealden epoch, what speculations 
would in all probability be hazarded to account for physical conditions assumed to 
be required by so marvellous a development in numbers and magnitude of the class 
Aves, to the almost entire exclusion of the Mammalia ! 
In attempting to explain the natural records of the ancient physical history of the 
globe and its inhabitants, by our acquaintance with the physiology, anatomy, and 
economy, of existing organic beings, we cannot be too often reminded of the caution 
of the sagacious Quetelet, that “our knowledge and our judgments are in general 
only founded on probabilities more or less great, which it is very important, but very 
difficult, to estimate at their just value.” 
In conclusion I would beg to remark, that in adding another genus of terrestrial 
reptiles to those previously established as belonging to the Fauna of the Wealden, I 
am fully aware of the imperfect manner in which, from various unavoidable causes 
— especially the pressure of professional duties — my investigations have been carried 
out. But encouraged in my earliest researches by the illustrious founder of Palaeon- 
tology, Baron Cuvier, and honoured by the highest award of the Geological Society, 
I felt reluctant to discontinue researches which no other naturalist seemed disposed 
to undertake, lest some important additions to our knowledge of the ancient physical 
condition of the earth and its inhabitants should be unrecorded and forgotten. 
Chester Square, Pimlico, 
November 1849. 
Description of the Plates. 
PLATE XXL 
The figures of this Plate are all on the same scale, which is •§• linear the natural size. 
Fig. 1. The right humerus of the Pelorosaurus Conyheari, obtained from the strata of 
Tilgate Forest in Sussex, by Mr. Peter Fuller of Lewes, and now in the 
possession of the author. 
1“. Anterior view. 
P. Posterior view. 
P. Transverse section of the shaft; m, the medullary canal filled with fawn- 
coloured sandstone. 
3 D 2 
