218 EXPLANATION OF PLATE. 



muzzle is extremely short, and the posterior region of the skull 

 is much developed. Pteroplax shows its relationship to Siren 

 by the reduction of the lateral cranial expansions, Batrachider- 

 peton by the large development of the occipital and parietal 

 bones, both also by the peculiar character of the prsemaxillas 

 and the deficiency of bony maxillae, though, as we have already 

 seen, there may be some doubt as to this last feature in Batra- 

 chiderpeton. 



EXPLANATION OF PLATE IV. 



Fig. 1- Dorsal view of the cranium of JBatrackiderpeton lineatwn, a little 

 enlarged ; the dotted lines indicate the restored parts : a, occi- 

 pital bones, bounded by raised lines ; b, inner cornua ; c, parietals 

 exhibiting foramen near the posterior part ; d, area circumscribed 

 by a circular groove, probably the frontals and nasals ; e, lateral 

 expansion ; /, one of the outer cornua ; g, supposed malar ; /*, 

 praemaxillaj, indicated in outline, in their supposed natural posi- 

 tion ; i, orbits, indicated by dotted lines. 



Fig. 2. View of roof of mouth of the same : a, inner cornua ; b, one of the 

 outer cornua ; c, left malar ; d, right malar, bent inwards ; e, 

 right pramiaxilla, doubled inwards ; f, free posterior extremity 

 of ditto ; #, teeth of the left prsemaxilla, bent inwards ; h, vomer 

 studded with minute teeth ; i i, two lateral rows of large vome- 

 rine teeth ; j, pterygoid ; k, an eminence, probably the sphenoid ; 

 /, two elevations, perhaps portions of the sphenoid, or possibly 

 the occipital condyles; m, occipital ridge; n, palato-temporal 

 foramen ; o, a depression, probably marking the position of the 

 right orbit. 



Fig. 3 View of the anterior portion of the left mandible, exhibiting the 

 teeth and surface-ornamentation : a, anterior extremity. 



Fig. 4. Three prcemaxillary teeth, seen in front, much enlarged. 



Fig. 5. Side view of one prajmaxillary tooth, much enlarged. 



Fig. 6. Much enlarged view of the apical extremity of the same, exhibit- 

 ing the striation. 



Fig. 7. Two of the small vomerine teeth, considerably enlarged. 



