2 riiOF. O. JJ. IKtWES AND MJv. il. II. «WmISrERTO^■ OX TilE 



ceplialia, whicli now, in its extended form, would appear to embrace a series of 

 genera and species occupying a truly central position among the terrestrial vertebrates. 

 Since the publication of Dr. Giinther's memoir on Sj)henodon, tlie discovery by Baur 

 and otliers of its vomerine tcetli, and by Spencer of its parietal-eye, have more especially 

 increased our knowledge of this remarkable animal beyond that which is ordinary. 

 One of its most distinctive characters is the forward prolongation of the pterygoids 

 to meet the vomers with apposition in the middle line. The mere forward prolongation 

 referred to is a feature already recognizable among the Batrachia and Stegocephalia ; 

 but special interest attaches to the median apposition, as there is little room for 

 doubt that in that there lies the clue to the reduction and suppression of the para- 

 sphenoid in the ascending series of the Amniota. This important Ehynchocephalian 

 character, long recognized in the Crocodilia and Dinosauria, has during recent years 

 been discovered in the Ichthyosauria ^ and the Plesiosauria ^ by Lydekker and others, 

 and probably in the Pterosauria by Newton ^, and it justifies the conclusion that 

 the living Sphenodon may be the sole surviving representative of an early and 

 widely ancestral amniote type. While the recent confirmation by Menzbier "* and 

 Pycraft'^ of Brandt's discovery in 1S39 '' that the Avian pterygoid may reach the 

 vomer, with their further demonstration, that while this is a permanent feature of 

 some RatitfE and the Tinamous among the higher birds, this Rhynchocephalian 

 character becomes lost during ontogeny under secondary segmentation and co- 

 ossification of parts, as the progressively modified facial skeleton comes into closer 

 relationship with the basis cranii, would seem to indicate an origin for the class Aves 

 from some more primitive reptilian type than might otherwise have been supposed '^ — 

 from something lower than the Dinosauria. Beyond this, Cope in 1870^, and Seeley 

 in 1874^, have drawn attention to certain Chelonian resemblances in the Rhyncho- 

 cephalia. In this they have been more recently followed by Boulenger, who regards ^^ 



' Lydekker, E. : Brit. Mus. Oat. Fossil Eept. & Amphib., Part 2, 1889, p. 5. Cf. also Baur, G. : Anat. Am. 

 Bd. X. 1895, p. 456 ; and (concerning the Ehjnchocephalian affinity) Americ. Nat. vol. sxi. 1887, p. 337. 



^ Lydekker, R. : originally in PL doUchodinis, ibid. p. 257. Cf. also Andrews, C. "W. : on Pehneustes, 

 Ann. & Mag. Nat. Hist. (6) vol. xvi. 1895, p. 248, and on " The Structure of the Plesiosaurian Skull " in 

 Jouru. Geol. Soc. vol. lii. 1896, p. 246. 



= Newton, E. T. : Phil. Trans, vol. 179 B. 1888, p. 503. 



" Menzbier, M. v. : Bull. Soc. Imp. Nat. Moscou (n. s.), tome i. 1887, p. 492. 



= Pycraft, W. P. : P. Z. S. 1893, pp. 973-974. 



" Brandt, J. : Mem Acad. Sci. St. Petersb. (vi.), Sci. Nat. tome iii. p. 81, & espec. pi. xvii. fig. 3 (Rhi/ncojis). 



' Provided the so-caUed " hemipterygoid " has the value claimed for it. It must not be forgotten that 

 Archaoptenjx appears to have had " abdominal ribs " (Dames, Palajontol. Abhandlg. Berlin, 1884, Bd. 2, 

 p. 144), and that " intercentra " occur in most of the groups of non-Passeres among living birds (Beddard, 

 P. Z. S. 1897, p. 465). 



" Oopo, E. D. : Proc. Americ. Assoc, vol. xix. 1870, p. 233. 



' Seeley, H. G. : Jouru. Linn. Soc, Zool. vol. xi. 1876. p. 183. 

 '" Boulenger, G. A. : Brit. Mus. Cat. Crocodilia and Chelonia, 1889, p. 1. 



