194 BRITISH FOSSIL REPTILES. 



articular process to a flat plate, from whicli tlie end is broken away. The advanced 

 tliicker end expands and extends into cross pieces, at right angles, each with an 

 articular depression indicative of clavicles. Now, these bones, which are absent in 

 Crocodilia, are present in higher Batrachia, and, in Bitfonidce, their mesial 

 extremities rest upon the expanded fore end of an episternal bone; it is not, 

 however, curved lengthwise as shown in fig. 10, in Labyrinthodon, a curvature 

 which indicates a greater vertical capacity of the fore part of the thoracic- 

 abdominal cavity. 



Sumerus. 



The fossil from the Trias at Coton End, of which four figures (11 — 14) are 

 given in Plate 6, is the proximal portion of a humerus. The moderately-convex, 

 proximal, articular end (fig. 14), from which extends the beginning of a well- 

 developed deltoid ridge, and the characters of the shaft shown by the surfaces 

 divided by that ridge, are more like those of the humerus of a toad than in that of 

 any Lacertian, Chelonian, or Crocodilian Reptile. The bone had a medullary 

 cavity of the width shown in fig. 13. 



If this limb-bone should belong to the same species as the ilium (figs. 16 and 

 17) the disproportion of size in the fore and hind limbs would be as in the 

 anourous Batrachians ; but I have received evidences of the tail of Labyrinthodon. 



Great part of the ilium is devoted to the formation of a large acetabular cavity ; 

 this is of an oblong form, extending in the long axis of the bone; its margin, 

 elsewhere sharp, is smoothed away at the base of the iliac body, which becomes 

 narrow and compressed as it recedes. The chief distinctive character is the 

 process above the acetabulum, from which it is separated by a smooth concavity ; 

 this process is compressed as it rises, and is bent forward, ending in an obtuse 

 point. A process of a different shape rises in a similar position above the 

 acetabulum in the frog. From the superacetabular process the ilium is continued 

 forward, and terminates in a thick subtruncate surface a few Unas in advance of 

 the acetabulum. The extent to which this ilium is articulated to the vertebra, at 

 least three in number, which may be regarded as sacral, is shown in the mesial 

 view of the bone given in fig. 17; the superacetabular process and the hinder 

 slender production contributing to the vertically concave articular surface. 



Of a femur, corresponding in size, in any degree, with the above ilium, I have, 

 as yet, received only the hemispherical head, represented in fig. 18. But in a 

 group of bones of a small, or possibly young. Reptile from the New Red Sandstone 

 (Trias) of Lymington, with the distal articular end of a femur (Batrachia, Plate 0, 

 fig. 1,/), were associated a tibia (t) and a humerus (''), plainly indicating a great 

 disproportion in size between the fore and hind limbs. 



