GENERAL STRUCTURE AND ORDERS. 



1039 



than the fore foot, some of those of the hind foot having a length 

 of eight inches. The absence of any known Dinosaurians from 

 the Bunter is strongly in favour of the Labyrinthodont nature of 

 these tracks ; and it has been suggested that those described as 

 Chirosaurus Barthi were made by T7-eviatosaurus Brauni of the 

 Bunter, the skull of which has a length of eight inches. If this 

 should prove to be the case, the name Trematosaurus would have 

 to yield to the earlier Chirosaurus. The largest tracks from the 

 Keuper of Cheshire have been described as C. Herculis. Other 

 tracks of feet from the Permian and Trias, which may be of Laby- 

 rinthodont origin, have been described under distinct names which 

 it will be unnecessary to quote. 



Order II. Apoda. — The remarkable limbless Csecilians being 

 unknown in a fossil state require no further mention. 



Order III. Caudata. — In this order the body is elongate, and 

 either lacertiform or anguiform, with a tail, and usually with two, 

 but occasionally only one, pairs of limbs. The cranium lacks the 

 postorbital, supratemporal, and supraoccipital bones of the Labyrin- 



Fig. 971.— Outlines of Siren (a), Amfihiuma (b), and Menobranchus (c). Reduced. 

 (After Mivart.) 



thodontia, and the palatines are approximated to the middle line, 

 and placed internally to the vomers and pterygoids. The ribs are 

 short, and the bodies of the vertebrae are either amphi- or opistho- 

 ccelous. The resemblance in the contour of the skull and the 

 short ribs to the Protritonidce suggests an affinity between the two 

 groups • but the position of the palatines is rather indicative of a 

 relationship with the Nyraniidce. 



