128 DR. J. E. GRAY’S SYNOPSIS OF THE SPECIES 
The chief difficulty in distinguishing the species has originated from the very great 
change of forms that takes place in the shape and proportions of the head of the animal 
in its different stages of growth; but the changes seem nearly similar in all the species, 
and therefore when once observed they can be easily allowed for. The difference may 
be divided into three stages, exemplified in the young, the nearly full-grown, and the 
adult or aged specimens. The head and beak of the young are generally depressed, with 
more or less distinctly marked symmetrical ridge and depressions; and these characters 
are gradually modified until the animal assumes its nearly full size,—the skull becoming 
thicker and more solid, but yet retaining most of the characters that distinguish its 
young state. After this period, as the animal increases in age, the skull becomes more 
and more convex and swollen and heavy, and assumes a very different external form. 
It is to be observed that in all these changes in the external form of the skull, the 
bones themselves of which it is composed preserve their general form and relation to 
each other ; and the sutures between these bones appear to me to offer some of the best 
characters to separate the species into groups. In many instances, when I have been in 
doubt, the sight of the intermaxillary suture has at once solved the difficulty, which has 
been verified by the examination of the locality of the specimen. 
These changes in the form of the head have been among the causes that have made the 
study of the species of Crocodiles so difficult. If this is the case with the recent species, 
how much more caution is requisite to determine the fossil remains of the animal! 
Cuvier set a very good example in that respect: he commenced the study of each group 
of animals with an examination of the osteology and external characters of the living 
species, and then applied the knowledge he thus acquired, to the distinction of the fossil 
remains; but now we often find paleontologists, as they call themselves, neglecting, or, 
at most, only taking the outline of the osteological and zoological characters of the living 
species at second hand, and describing the fossil, and often forming genera and species 
on-a small fragment, thus encumbering the science with a multitude of names. 
At one time I proposed to give accurate measurements of the different parts of the 
713. Crocodilus acutus=Oopholis porosus of India. 
715. Crocodilus acutus= Crocodilus vulgaris of Africa. 
717. Crocodilus vulyaris, much distorted. 
718. Crocodilus vulgaris=Bombifrons, perhaps B. siamensis. 
719-724, 727, 728. Crocodilus biporcatus=Oopholis porosus. 
725. Crocodilus biporcatus= Crocodilus vulgaris. 
5 
So 
6. Crocodilus biporcatus = Bombifrons indicus. 
0, 751. Crocodilus rhombifer, from Bengal= Bombifrons indicus. 
2. Crocodilus palustris ?= Bombifrons indicus. 
30-762. Alligator lucius= Alligator mississippiensis. 
764, Alligator niger=Jacure nigra. 
Dr. J. E. Gray “ On the Change of Form of the Heads of Crocodiles,” Transactions of the Sections in ‘ Report 
of the British Association of Science,’ Cambridge, 1862, p. 109. 
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