CHELONTA. 



CHELONIA. 



982 



are the palatines, surrounded behind and externally by the pterygoid 

 bones, which last extend along the external border of the palatine to 

 the maxillary bones. The rest of the pterygoids covers the lower 

 surface of the cranium between the two tympanic cavities and the 

 two temporal ala;, leaving exposed to view behind only a triangular 

 part of the body of the sphenoid. The olfactory and optic nerves 

 have their exit by the cartilaginous septa of the cranium, and not by 

 any particular opening in the skull. Cuvier thinks that it is the 

 same with the third and fourth pairs : the sixth goes forth by a 

 small caual of the body of the sphenoid bone. The fifth pair has 

 a great hole between the petrous bone and the temporal ala divided 

 into two externally. There is at the external border of the palatine 

 bone a hole analogous to the pterygo-palatine. 



Internally, the cerebral cavity is higher than it is wide; the bottom 

 of it is very entire : but, in front, in the sphenoid, there is a deep 

 fosset for the pituitary gland, a kind of saddle. From the sides of 

 this part spring the cartilaginous septa, which in going to form a 

 j unction with the ante-cerebral partition of the frontal bone, close the 

 cavity of the cranium, support the whole anterior part of the 

 encephalon, and occupy the place of the cribriform plate, of the orbital 

 alee ; or otherwise, the anterior sphenoid, and the greater part of the 

 temporal ahe, of which another considerable part is replaced by the 

 descending portions of the parietal, so that what remains does not 

 participate in the formation of the chamber of the cranium except a 

 little in front of the hole for the fifth pair of nerves. There is no 

 more bony trace of the anterior sphenoid than in the crocodile. 



In the Emydei, or ordinary Fresh-Water Tortoises, the head is more 

 flattened. The principal frontals, although they are wider than they 

 are long, do not always reach to the border of the orbit, as is, for 

 example, the case in the Tettndo (Caludo) Europtfa ; the posterior 

 frontal is wider. The frame of the tympanum is not complete, and 

 in lieu of a hole there is a fissure for the passage of the ossiculum 

 auditus from one hollow of the cavity to the other. The basilary and 

 palatine regions form but one plane ; the palatines not being even 

 concave. Cuvier observes that Testudmea scripta, picta, icabra, 

 dnnala, ccntrata, damn, and riryulala, belong to this category. 

 Certain Emydet, he remarks, Emyi esiMwia for instance, tend to the Sea- 

 Tortoises, or Turtles, and the Fresh-Water Tortoises, and yet exhibit 

 characters peculiar to themselves. 



In the Trionyca, or Soft Tortoises, the skull is depressed, and 

 elongated backwards ; the muzzle, pointed in certain species (that of 

 the Nile for instance), is short and rounded in some others. The 

 intermaxillary bones are very small, and have neither nasal nor 

 palatine apophysis ; there is In-hind them a large incisive hole. The 

 maxillaries unite upon the palate for a rather long space, so that the 

 posterior nostrils are more backwards than in the Land-Tortoises. 

 The palatines do not unite below to prolong the palate ; they are 

 hollowed into a demi-canal anteriorly, and less extended than in the 

 Land-Tortoises. 



The principal character of the Marine Tortoises, or Turtles, is that 

 a lamina of their parietal, their posterior frontal, their mastoidean, 

 their temporal, and their jugul, unite together, and with the tympanic 

 cavity, by sutures, to cover the whole region of the temple with a 

 bony roof, which has no solution of continuity. Their muzzle being 

 shorter than in other tortoises, and their orbits much longer, their 

 nasal cavity is smaller, and as wide as it is high and long. Ita 

 posterior wall belongs entirely to the anterior frontals, and it is 

 between them that the olfactory nerves are introduced. The bony 

 tubes of the back nostrils commence in the lower part of this 

 posterior partition, and, like the palatines, have a palatine part or 

 lower lamina ; these tubes are rather longer, more directed backwards, 

 and bear less resemblance to simple holes. It results also from the 

 size of the orbit that the inter-orbital membranous or cartilaginous 

 space is more extended. 



The most heteroclite skull among the tortoises is that of the Mata- 

 mata (Tatiulo fmbriata, Chdy JimbrifUa). Extraordinarily large and 

 flat, it seems to have been crushed. The very small orbits are close 

 to the end of the muzzle. The posterior region of the cranium is 

 elevated ; and the two tympanic bones, in form of trumpet*, widen 

 out on each side of the cranium. The temple is a wide horizontal 

 fossa, not deep, and not at all covered, except behind by the union of 

 the posterior angle of the parietal with the mastoidean bone ; and, 

 what is peculiar, Cuvier observes, to this sub-genus, this fossa is not 

 framed in externally, because there is no temporal bone, or at least 

 it is reduced to a simple vestige. The two maxillaries form together 

 a transversal arch, in the middle of which, below, is a single inter- 

 maxillary, and, above, the external aperture of the nostrils, which is 

 continued into a small fleshy proboscis. The two palatine bones, and, 

 between them, the vomer, fill below the concavity of this arch, and 

 have in front the two back nostrils well separated, but which the 

 palatines do not encircle below. At the posterior border of the 

 palatine is a rather large pterygo-palatine hole. The anterior and 

 posterior frontals form the upper part of the orbits. The principal 

 frontals advance between the anterior frontals to the edge of the 

 external nostrils. There is no more nasal bone than in the other 

 tortoise*. The jugal proceeds from the posterior angle of the orbit 

 between the maxillary and posterior frontal, beyond which it does not 

 go, touching a little behind nnd below the pterygoidean ; but not 



forming any projection behind to border the temple. This last is in 

 this manner separated from the orbit by a postorbital branch of 

 excessive width, and which takes in the totality of the posterior 

 frontal and the jugal boues. The posterior frontal articulates itself 

 to the pterygoideau by its external posterior angle. The rest of its 

 posterior border is free, and is continued with that of the parietal 



Skull of Matamata (Chelyt fimliriala). 

 1, seen from mbovc ; 2, seen from below ; 3, profile ; 4, seen from behind. 



to cover a wide and flat canal of communication, proceeding from the 

 temple to the orbit, and formed below by the pterygoirlean and 

 palatine bones. The two pterygoideans are enormous. They form 

 the greatest part of the base of the cranium and of the bottom of 

 the temple. Their external border is curved in its anterior part for 

 its continuation with the free border of the posterior frontal ; there 



