LIASSIC FORMATIONS. 



61 



to the unbiassed investigator, and, indeed, becomes plainly his business, to determine, not 

 merely whether Avian or Saurian characters predominate in the Pterosaurian skull, but to 

 define the degree of affinity or correspondence of cranial structure therein traceable to 

 such structures in Enaliosauria, Dinosauria, Bicynodontia, Crocodilia, Lacerlilia, each of 

 u^hich may be a group, organically, of co-ordinate value with Avcs. 



Greater respect to the memory of so imbiassed a seeker after truth cannot be shown 

 than by weighing with due care and what judgment one may be able to bring to the task 

 the value and significance of each well-determined evidence of the cranial structure which 

 Von Meyer has described and reasoned upon. 



It is to be regretted that not in any of the numerous figures of the skull of Ptero- 

 sauria, original or copied, has Von Meyer indicated the bones which he describes. When 

 he writes — " The temporal bone lies external to the parietal and principal frontal bones, 

 and mainly forms the temporal fossa," ^ one much wishes he had indicated his ' Schliifen- 

 bein ' in the skull of Mhamphorhynchus Gemmingi, pi. iii, fig. 4 ; pi. ix ; pi. x, fig. 1 ; 

 or in the more instructive example of cranial structure which he has borrowed from 

 Goldfuss for the subject of his pi. v {Pterodactylus crasdrostris). 



By ' Sclilafenbein ' Von Meyer may mean that element of the compound ' temporal 

 bone' of anthropotomy which I have called 'squamosal.' No doubt in Man and 

 most Mammals the squamosal does contribute a notable share to the formation of the 

 temporal fossa, whence the name ' temporal ' given to the incongruous group of cranial 

 elements coalescing in such warm-blooded Vertebrates with the squamosal, so exceptionally 

 expanded in the Mammalia. But as to the value of the bed of the temporal muscles in 

 determining the homology of the bones forming it, I would refer to the remarks in my 

 work on the ' Homologies of the Vertebrate Skeleton.' ^ 



Some clue to the bone signified by Von Meyer may be got from the following remarks — ■ 

 " Anteriorly it seems not to take, as in Birds, a share in the formation of the orbital rim ; 

 here, much more as in Saurians, it is pushed aside or supplanted by the postfrontal." ^ 



The term ' temporal bone ' (Schliifenbein) has been used in various senses, but 

 whether it be applied to that element which I, with Cuvier, call ' mastoid ' in Beptilia, 

 or to that which others,* with Cuvier, call ' temporal ' (meaning squamosal) in Birds, 

 there is no bone that Von Meyer can be supposed to mean by ' Schlafenbein ' which 

 forms any part of the rim of the orbit in Birds. 



Von Meyer recognises a ' postfrontal ' (' Ilinterstirnbein ') in Plcrosauria, and states 

 that it pushes away his temporal (Schlafenbein) from the orbit. In Pterosauria the post- 



1 " Das Sclilafenbein liegt aussen an dem Scbeitelbein unJ Haiiptstirnbein, und bildet haupl.-aciilich 

 die Schliifengrube." — Op. cit., p. ITj. 



2 8vo, 184S, p. 33. 



^ " Vorn scheint es nicbt wic in den Viigeln an dcr Biklung des Augcnholilenrandes Tlicil za lulnneu, 

 bier vielmehr wie in den Sanriern duich das Ilinterstirnbein verdriingt zu werden." — Op. cit. p. 15. 

 ♦ Hallman, "Die vergleicbeude Osteologie des Scbliifenbeins," p. 8, pi. 1. 



