OF THE SKULL IK THE COMMON SNAKE. 
415 
end, the suture being vertical ; this is the anomalous position of the true coronoid 
region ; the two bones are very similar, but their points look in opposite directions. 
These two bones hide the shrivelled remains of Meckel’s cartilage ; none of these 
bones of the mandible are dentigenous except the dentaries, and only the palatines 
and pterygoids and maxillaries above. 
Of the hyoid or second post-oral arch I can only find two rudiments, and these have 
lost their independence ; the antero- superior or hyo-mandibular element is now the 
small columellar prickle on the oval stapedal plate (Plate 33, fig. 2, co.). 
The other, or postero- inferior, piece is starved and useless ; it is ankylosed to the 
inner face of the quadrate, towards the back of the upper third (Plate 32, fig. 2, sl.h ). 
This is all that remains of the stylo-cerato-hyal bar ; at least I have failed to find any 
cartilage in the distal or lingual region. 
Concluding Ren ici? ds. 
I have carefully studied the skulls in the ripe young and the adult of Lacertians, 
Chelonians, and the Crocodiles, but time has not served for working them out from 
their early stages. 
Materials are ready for the Lacertians and their sub-group, the Anguians. Early 
embryos of the Tortoise'" and Crocodile are still wanting ; yet this present piece of 
work, it is to be hoped, will be of considerable use. It will serve me as a lantern with 
two windows : letting light backwards upon the Ichtliyopsida and forwards on to the 
nobler Reptiles ; and it will light up even the winged Fowls that, in their perfectness, 
seem to have exhausted the possibilities of the Sauropsidan type.t 
Description of the Plates. 
PLATE 27. 
Fig. 1. First stage. Side view of Embryo of Common Snake ( Tropidonotus natrix), 
whose total length was § inch. X 17 diameters. 
Fig. 2. Head of the same, severed and slightly bent back (straightened) ; lower view. 
X 17 diameters. 
Fig. 3. Second stage. Side view of the head and neck of an older Embryo, measuring 
about 1 inch in length. X 16 diameters. 
* Since the above was written, I have received from Sir Wyville Thomson several large, and from 
Mr. Moseley many small, embryos of this important type. 
f The use which I have made from time to time of the Snake’s skull may be seen by reference to various 
papers on the Structure and Development of the Bird’s Skull in the Transactions of the Royal, Linnean, 
Zoological, and Microscopical Societies. In the Snake’s skull, ichthyic elements are curiously specialized ; 
in that of the Bird the same parts re-appear, but in most remarkable metamorphic combinations. 
M DCCCLXX VIII. 3 II 
