OP A HTGHEE POEM OP LIFE Otf A LOWEE POEM. 425 



ference as to the concomitant valvular structures of the soft parts in 

 those extinct proccelian species. 



These considerations stimulated or augmented the desire to deter- 

 mine the palatal character of the fossil skulls of those Crocodilia of 

 the newer Mesozoic formations which, in the massive proportions of 

 their jaws, made the nearest approach to the Tertiary and modern 

 kinds. Such demonstration of the structure of the bony palate is 

 accordingly given in the specimens of the Purbeck Crocodiles in the 

 British Museum, which form the subject of my " Monograph on 

 British Fossil Reptilia," in the volume of the Palaeontographical 

 Society for 1878. 



Although the jaws of Goniopholis crassidens and Goniopholis simus 

 have proportions "adapted to grapple with large and active mammals, 

 the evidence of any such warm-blooded air-breathers coexistent 

 with those Crocodilia is not yet acquired. And the probability of 

 such coexistence is, in my opinion, very small, from the circumstance 

 of the palato-nares being relatively larger and more advanced than 

 in the Crocodiles contemporary with such mammals. The palato- 

 nares in Goniopholis open likewise upon a horizontal plane, look 

 directly downward, not obliquely forward, and, moreover, have 

 a different anatomical conformation. Instead of being formed or 

 bounded by the pterygoids exclusively, as in Tertiary Crocodiles, the 

 palatine bones enter into the formation of the anterior third of the 

 circumference of the palato-nares. 



With this anatomical character, which I am disposed to associate 

 with a fish diet, are combined, in both Goniopholis and Petrosuchus. 

 upper temporal apertures larger than the orbits and amphiccelian 

 or amphiplatyan vertebrae. 



Now all known Tertiary and existing Crocodilia combine with 

 small, posterior, pterygoid palato-nares, upper temporal apertures (fig. 

 2, t) less than the orbits (ibid, o) ; and in some broad-faced kinds the 

 upper temporal apertures are almost obliterated by the progressive 

 increase of the osseous roof of the temporal vacuities. These vacui- 

 ties, in the recent reptile, are occupied by the temporal muscles, 

 and the power of these biting and holding muscles is in the ratio of 

 the extent of their bony origins. 



In the amphiccelian fish-eating Crocodilia, the upper temporal 

 apertures (fig. 5, t) are larger, and usually much larger, than the 

 orbits (o) ; and they are, for the most part, associated with slender 

 jaws and with numerous, small, uniformly sized teeth (fig. 4). 



With the palatine modifications which relate to the drowning of 

 air-breathing prey, and with the cranial developments which relate 

 to the grip of such prey, we find, as a rule, in proccelian Crocodiles, 

 concomitant modifications in the breadth (fig. 2) and strength of the 

 jaws, in productions of the alveolar borders, and in the size of the 

 teeth (fig. 1). There is also inequality of size, favouring holdfast, 

 as in mammalian Carnivora ; and certain teeth of the dental series 

 have accordingly received the name of canines in the Crocodiles 

 with such analogous dentition. 



In this comparison and its applications I propose at present to 

 Q.J.G.S. No. 134. 2p 



