260 FOSSIL REPTILES. 



nian reptiles, is, that a lamina of the parietal, the anterior fron- 

 tal, the mastoid, the temporal, and the j'lgal, unite together, 

 and with the os tympani by sutures, to cover all the region of 

 the temple with an osseous penthouse uninterrupted in its con- 

 tinuity. Their muzzle being much shorter and the orbits much 

 larger than in the other tortoises, the nasal cavity is smaller, 

 and of equal width, height, and length. Its hinder paries be- 

 longs entirely to the anterior frontals, and between them is the 

 introduction of the olfactory nerves. The osseous tubes of the 

 back-nostrils commence in the lower part of this hinder paries, 

 and as the palatines have a lower lamina, these tubes are a little 

 longer, directed more backwards, and have less resemblance to 

 simple foramina. 



From the size of the orbit it also results that the inter-orbital 

 membranous or cartilaginous space is more extended. The 

 piece which we regard as the temporal wing is singularly small 

 in the chelonia my das, altogether at the external face, and sim- 

 ply pasted on the suture of the descending portion of the parietal 

 with the pterygoid. 



The auricular osselet does not pass through a foramen, but 

 by a wide emargination, from the first chamber of the tympa- 

 num into the second, and this second chamber is cartilaginous in 

 all its hinder paries. By the same emargination the Eustachian 

 tube descends towards the back part of the mouth. The first 

 chamber of the tympanum is not very concave. There is, pro- 

 perly speaking, no mastoidean cellules. But the bone of that 

 name completes the roof of this chamber, and thus extends its 

 concavity. The foramen of the fifth pair is oval and very large, 

 between the descending portion of the parietal, the pterygoid, 

 and the os petrosum. 



The most anomalous head of tortoise is that of theMATAMATA 

 (testudo fimhriata) . It is so singularly broad and flat, that it 

 has the appearance of having been crushed. The orbits are 

 extremely small, and very near the end of the muzzle. The 

 hinder region of the cranium is elevated, and the two tympanic 



