66 PKOF. G. B. HOWES AND Mlt. 11. H. SWINNERTON ON THE 



temporal arcli of the Squamata represents only the upper arch of the Rhynchocephalia, 

 basini^- his conclnsions on the surmise that the quadra to-jugal is not unrepresented in 

 the former as is usually supposed, but that the bone generally termed the "squamosal" 

 is its homologue. Somewhat similar conclusions follow from the later determinations 

 of Gaupp, laborious but unconvincing, in which he seeks to show i that tlie bmie 

 hitherto known as the quadrato-jugal in Batrachia and Birds must be for the future 

 termed the " quadrato-maxillary," and that for the quadrato-jugal in Crocodilia, 

 Chclonia, Rhynchocephalia, and Laccrtilia, the term " paraquadrate " must be 

 employed. 



Baur assumes that the Squamata " never possessed an infra-temporal fossa, but that 

 the broad arch was reduced from below in the same way as in the Testudinata " {op. cH. 

 p. 473). It is beyond the scope of this memoir to fully discuss this question, 

 voluminous in itself, but there tells strotigly against the interpretation of the bone 

 which in the " Squamata " reaches the head of the quadrate with that which in the 

 Rhynchocephalia flanks its lower articular border, the fact, long ago pointed out by 

 Huxley ^, that in the living Lacertilia there is present a ligament having the relation- 

 ships of the latter. And, further, argument by analogy to the living Urodela, in 

 which, while the maxillo-jugal arch is complete in bone only in the Eastern genus 

 Tylototriton •^, a similar representation is present in ligament which may extend even 

 into the maxillary region, places a further obstacle in the way of its acceptation. All 

 recent investigation has gone to show that the Reptilia and the Batrachia are the 

 diversely modified descendants of the Stegocephalia ; and the fact that in them the 

 supra-temporal, squamosal, and quadrato-jugal coexist in a transverse series tells with 

 great force against this seductive argument. 



The " Seyto-maxillary.''' — This bone was originally described in Sphenodon by Osawa 

 (98 ". p. 503) as a small semicircular element attached by fibrous tissue to the vomer, 

 and he therefore named it a " turbinal." In this he was unquestionably in error. The 

 bone was figured and described by Parker in Zootoca** as the septo-maxillary, and 

 under this name it has been more recently described by Gaupp in other lacertilian 

 embryos. Concerning its detailed relationship, he associates it with the support of the 

 septum nasi internally and with that of the border of the cartUage enclosing Jacobson's 

 organ superficially {op. cit. Ber. p. 10). The bone present in Sphenodon (PI. IV. fig. 2, 

 s.mx.) is still more superficial in position and free of the nasal septum than this. In 

 consideration of the fact that whereas here the Jacobson's organ is completely roofed in 

 cartilage, in the lizard, according to Parker, the septo-maxillary fulfils that function^, 



^ Gaupp, Gr. : Morphol. Arbeiten, Jena, Bd. iv. 1895, p. 77. 



- Huxley, T. H. : Anat. of Vertebr. 1871, p. 190. 



= Eiese, H. : Zoolog. Jabvb., Anat Abth. Bd. v. 1892, p. 99. 



■• Parker, W. K. : Phil. Trans. 1879, pt. ii. p. 609. 



" Parker, ^X. K. : Phil. Trans. 1S79, pi. 44. fig. 5. 



