4o6 DA VI SON. [Vol. XI. 



tilage, is explained by the anatomy of the young, in which the 

 lower jaw is relatively shorter than in the adult. A similar 

 abbreviation of the lower jaw is exhibited by the majority of 

 the Gymnophiona, as shown by Wiedersheim (Taf. V, Figs. 58 

 and 59). 



The vertebrae of AmpJiiiuna are highly specialized, having 

 definite processes for the attachments of its complexly con- 

 structed trunk musculature. As Cope has already suggested, 

 the prominent anterior hypapophyses are peculiar to the Coc- 

 cilians and A^nphiiima. Thus far I have pointed out the features 

 in these two families which give evidence of genealogical affinity. 

 The proof of relationship furnished is to my mind conclusive ; 

 but the gravest question — what that relationship is — remains 

 to be answered. If Huxley's dictum, " It is more important 

 that similarities should not be neglected than that differences 

 should be overlooked " were maintainable, near afhnity of these 

 two families must be admitted. Before such affinity can be 

 asserted, important contrasts in skull structure must be ex- 

 plained. Thus Kingsley says : " The presence of an ethmoid 

 in the GymnopJiioma (and its absence from AvipJiijtma and 

 other Urodeles), the existence of a turbinal, the absence of a 

 parasphenoid, and the presence of a basisphenoid are all points 

 of importance." Another striking contrast is seen in the struc- 

 ture of the orbit which is only partially encircled by the bony 

 elements in Amphiiuna, there being no jugal or quadrato-jugal 

 bone present. Gervais gives a concise description of the coe- 

 cilian orbit : " Cependant I'orbite des Cecilies n'est percee ni 

 dans le maxillaire seul ni dans le corps de I'os jugal ; c'est ce 

 que Ton voit tr^s-bien sur la tete d'un jeune animal de ce genre; 

 et avec quelque attention, surtout en se servant d'une loupe, 

 on retrouve meme chez I'adulte des traces de la suture des 

 deux OS entre lesquels I'oeil est ici place, et qui concourent, 

 comme chez beaucoup d'autres animaux, a former un cercle 

 orbitaire." These differences in skull structure make it patent 

 that AmpJiijima cannot be the connecting link between the 

 leg-bearing Urodeles and the Coecilians, as Cope has asserted. 

 The elongated cranium, the double series of teeth, the ten- 

 tacular apparatus, the degenerated optic sense, the manner of 



