Labyrinthodon /rom Warwickshire. 533 



the anterior part of the transverse process must be regarded as a corresponding 

 structure with that more extensive fissure which separates the anterior part of the 

 transverse process from the base of the oblique process in the smaller vertebra. It 

 is, therefore, a modification to which attention should be paid in examining verte- 

 brae or portions of vertebrae from the New Red Sandstone. 



Bones of the Extremities. — The fossils to be noticed under this head are few, but 

 significant. 



I am disposed to refer to the anterior extremities the proximal end of a long 

 bone (PI. XLV. figg. 11-15.), which presents all the characteristics of the cor- 

 responding part of the humerus of a Toad or Frog ; viz. the convex, somewhat 

 transversely extended articular end, the internal longitudinal depression, and the 

 well-developed deltoid ridge. This fragment, which includes perhaps the upper 

 half of the bone, is two inches in length and thirteen lines in breadth ; it dimi- 

 nishes, chiefly by the subsidence of the deltoid crest, to a subtrihedral shaft with 

 the angles rounded off; it presents moderately thick compact walls, with a central 

 medullary cavity. In this structure, as well as in its general form, the present 

 bone agrees with the Batrachian and differs from the Crocodilian type. 



Right Ilium. — The most complete bone in the present collection, not belonging 

 to the cranial series, is the right ilium (PI. XLV. figg. 16. and 17.), which pre- 

 sents, like many of the previously described bones, a combination of Crocodilian 

 and Batrachian characters. It is nearly six inches in length, and is therefore most 

 probably referable to the same species as the jaws last described. It supports on 

 its anterior and outer surface the same proportion of the acetabular cavity as in 

 the Crocodiles. This cavity is bounded on its upper part by a produced and sharp 

 ridge, as in the Frog ; which ridge is not emarginate at its anterior part, as in the 

 Crocodile, but it subsides at the posterior part of the cavity, the surface of which 

 is here continuous with the outer surface of the produced posterior part of the 

 bone. 



Above the acetabulum, in the Frog, the ilium gives off" a broad and depressed 

 process, the lower extremity of which is separated from the acetabulum by a smooth 

 concave groove ; there is no such process or groove in the Crocodile, but only a 

 slight rising of the upper border of the acetabulum, against which the sacral ribs 

 abut. In the present ilium there is a well-marked process in the analogous situa- 

 .tion to that in the Frog, and separated also by a smooth concave surface from the 

 upper edge of the acetabulum, but this process, instead of being depressed, is com- 

 pressed and curved forwards ; its internal extremity is pointed and bent, repre- 

 senting, as it seems, the rudiment of the long anterior process of the ilium in the 

 anourous Batrachia. This process, in the Labyrinthodon, does not attain the par- 

 allel of the anterior margin of the acetabulum ; and the bone terminates in a thick 



VOL. VI. — SECOND SERIES. 3 Z 



