^04 Dr. Francis Baron Nopcsa — British Dinosaurs. 



bone iu Cnmptosanrus, Mochlodon, Iguanodon, or Telmatosaurus, but 

 rather reminding one of the Compsognalkus or Thecodontosaurus type ; 

 and the dowmoard direction of the foramina by which the cranial 

 nerves pass out from the brain-cavity along the basal and lateral 

 elements of the skull is an especially bird-like feature. Describing 

 the basi-occipital and basi-sphenoidal elements in Mochlodon, I stated 

 these elements in Gresshjosaiir as are in the same relation to the same 

 parts in Zanclodon as are those of Mocldodon to Telmatosaurus, and 

 thus I could distinguish a Mochlodon - Gresslyosaurus or elongated 

 and a Telmatosaurus- Zanclodon or abbreviated type. To this now 

 a third type, the Hypsilophodon-Thecodontosaiirus or bird-like type 

 has to be added. The great phylogenetic and physiologic value of 

 this fact, throwing much light on the relationship of Dinosaurs and 

 birds and also on Dinosaur evolution itself, will be more fully 

 explained on some other occasion. 



Supra-occipital bone (p. 207, Fig. 2). As it has some years ago been 

 doubted by Professor Koken that in Ornithopodida3 the supra- 

 occipital enters into the foramen magnum (Neues Jahrb. f. Min. 

 Geol. u. Pal., 1901, vol. i), it seemed desirable to settle also this 

 question, and therefore a drawing of this part of another Hypsilophodon 

 skull is also given. It will be seen at once that the supra-occipital 

 contributes largely to the boundary of the wide foramen magnum, 

 and that it rises very much in the same way as in Hatleria or 

 Compsognathus, forming at the same time a sharp median posterior 

 crest. The diiferences from the Acanthopholis or even the Iguanodon 

 type are easily noticed. The processus parotici are not raised as in 

 Telmatosaurus, but at the same level as the foramen magnum, and, 

 showing at once where the missing squamosals are to be sought for, 

 this indicates that the quadrate bone was comparatively short, that 

 the superior temporal openings were visible from the side, and 

 proves the presence of large hypoparotic fossae. 



Predentary. Although this bone is of quite exceptional interest, 

 and was alreadjf described by Hulke in his monograph on Hypsi- 

 lophodon, yet it never has been figured. Hypsilophodon is, as far as 

 we know, the single Dinosaur in which a tooth bearing a prse- 

 maxillary comes to bear down on a predentary bone, and this is the 

 reason why in p. 207, Fig. 3, an enlarged drawing of this element is 

 given. 



Dollo remarked some years ago that a toothed prcemaxillary 

 might well correspond to a tooth-bearing predentary, and I perfectly 

 agree with the famous Belgian professor that this is exactly the 

 thing one ought to expect if the predentary of the Orthopoda were 

 an entodermal ossification and homologous with the same bone in 

 Aspidorhynchus, Ampliignathodon, or in human anatomy. 



Working along quite other lines of research than Professor Dollo, 

 I, however, recently came to the result that the j^redentary of 

 Orthopoda cannot have been derived from a cartilaginous source, 

 but must simply be regarded as a dermal ossification (Denksch. 

 Akad., Vienna, 1904). The paradoxical fact that in Hypsilophodon 

 an edentulous predentary meets a toothed preemaxillary is, as far as 



