26 Mr. H. G. Seeley on the Structure of 



that organ shrinks away from the optic lobes. Still the dif- 

 ferences are only of proportion of parts, and not peculiarities 

 of arrangement. But Avhcn the brain is seen from the side, it 

 shows characters which are altogether peculiar to it, in the 

 development of the under part of the cerebrum, by which that 

 part of the brain attains a larger size than any thing seen in 

 birds, and more in accord with the highest mammals than 

 with other animals. Here, of course, the question arises, Is 

 it certain that the parts have been con-ectly determined (in 

 dealing with such material the question is inevitable), and 

 that what have been called optic lobes are not lateral lobes 

 of the cerebrum, so that, after all, tlie animal may be a mam- 

 mal ? I can only reply that Avhen the Pterodactyle's skull is 

 compared with the bird's skull, the correspondence of the parts 

 called optic lobes is very close. They are sunk deep into the 

 alis})henoid and squamosal bones, so as to be covered by the 

 thinnest possible film of bone externally, as in birds ; a sharj? 

 bony ridge divides them from the cerebrum, as in birds ; they 

 are as prominent and subhemispherical as in birds, and they 

 are situated almost as in birds ; while I fail to find this bony 

 definition of outline in the encasement of the similarly placed 

 part of the mammalian cerebrum ; so that I have no doubt at 

 all that these parts of the brain are accurately described by 

 the lettering in the description of Plate II. Eveiy facility is 

 offered at the Woodwardian Museum for the examination of 

 the specimens. 



And the conclusion which follows from the facts detailed is 

 that these Ornithosauria, while having a brain moulded upon 

 the bird-type, attained to a condition of cerebral develo})ment 

 which would raise them, so far as evidence from the brain 

 went, above birds. In fact, this brain, if brain-fonn is worth 

 any thing in classification, proves that these animals must take 

 rank immediately above birds, in the same natural group with 

 them. 



Now it will be attempted to reconstruct the Ornithocheiroid 

 skull in which this brain was lodged * ; and to this end follows 

 a description of what may be regarded as the maxillarv' bone. 

 (PI. III. figs. 1, 2.) 



Like all Pterodactyle bones, it is fractured. It is a sub- 

 triangular squamous bone, flat externally in antero-posterior 

 direction, perfectly smooth, and very slightly convex from 

 above downward, If inch long at the palatal border. Above 

 this fractured border is an impressed area less than ^ an inch 



* The best general restoration of the Oraithosaurian skull is Prof. 

 Owen's, given in pi. 27 of his memoir in the Palaeontographical Society's 

 volume for 1851. 



