298 Herr F. Siebenrock on the 



ill llie adult, a point which was hitherto in doubt ; while there 

 will also be appended further communications upon the 

 subject of the dentition of the vomer. 



I. 



The interorhital septum and the anterior cranial wall of 

 //a^^^rm were represented by G.iinther* and Briililf as Ikjiuo- 

 geneous cartilaginous structures, without further allusion 

 being made to them in the text of their papers. If, however, 

 these parts be examined more closely in a carefully prepared 

 JIatterta-head, it is found that neither the interorbital septum 

 nor the anterior cranial wall are uniformly developed, but 

 that in both cartilaginous structures occur, just as they are 

 met with in the majority of Saurians with a distinct inter- 

 orbital septum. 



In the interorbital septum of Hatteria the anterior and 

 upper edges are sinuous, while the lower one is straight. 

 The posterior edge is notched and forms the anterior boundary 

 of the optic foramen. In the majority of lizards the inter- 

 orbital septum is membranous, and in it is embedded the 

 cartilaginous plate which has developed from the two lower 

 trabcculffi (" unteren Schiidelbalken "). In Hatteria, how- 

 ever, the entire interorbital septum is cartilaginous, with the 

 excejition of an oval fenestra at the upper margin, which is 

 covered by a membrane. But since the cartilaginous plate in 

 the interorbital septum in the case of the other lizards repre- 

 sents the presphenoid, in Hatteria the entire interorbital 

 septum must receive the same interpretation. 



A much greater degree of complication is presented by the 

 cartilaginous structures in the anterior cranial wall, with 

 regard to which Gunther writes [loc. cit. p. 5) : — " A cres- 

 centic sjnice between alisphenoid and columella remains 

 cartilaginous ; and the fore part of the cranial cavity is ckised 

 by fibro-cartilaginous membrane without a trace of ossifica- 

 tion." It is perfectly correct that a bony orbitosphenoid is 

 not present in Hatteria, but in its stead we find a cartila- 

 ginous one, which exhibits the same arrangement as in all 

 other lizards. It is remarked by Baur |, in a note upon 

 Sphenodon — Hatteria, that the alisphenoid-orbitosphenoid is 



* A. Gunther, "A Contribution to tlio Anatomy of Ilntteria," Phil. 

 Trans. Rov. Soc. Lond. 18G7. 



t C. B.'lhubl, 'Zootomie nllfr Thierclasseu," Taf. 148 and l-i;). with 

 cxphination. 



X (i. Uaur, " O.-teolojrischi' Notizen iiber Reptilieu (Fortsetzuug vi.)." 

 Zool. Anzeitror, xii. Jahrg., 188i>, p. 4-5. 



