"206 Dr. Francis Baron Nopcsa — Britkh Dinomurs. 



Liassic Scelidosaurns. It is to be remarked that (1) the rhomboidal 

 arrangement of these tendons described in lynnnodon seems to be 

 absent in Hypsilopliodon as well as in the North American Claosaurus ; 

 (2) that in Iguanodon these ossifications are absent under the 

 diapophysis, while in Hypsilopliodon they are present also on this 

 place, and form thus on each side of the tail two bundles which 

 run along the neurapophyses and the chevron bones. Besides this 

 the ossified tendons attain in Iguanodon their maximum of develop- 

 ment in the lumbar region, while in Hypsilopliodon their number 

 augments the nearer we approach the end of the tail, so that this 

 region is entirely ensheathed. The physiological value of such 

 a rigid organ, already unexplainable in Iguanodon, becomes in con- 

 sequence entirely a puzzle. 



Fourth trochanter. Though the fourth trochanter of Hypsilophodon 

 was already well figured and described by Hulke, I still feel induced 

 to mention also this part, since Hulke in the Neues Jahrbuch fiir 

 Jlineralogie expressed some time ago his doubts about the con-ectness 

 of my assertion that the ' trochanter pendant ' represents a more 

 primitive stage in evolution than the ' trochanter en crete.' Now 

 I find that the trochanter pendant of Hypsilophodon just seems 

 to prove the correctness of my original view. In Hypsilophodon 

 the fourth trochanter is comparatively much broadet" than in Campto- 

 sanrus, where it also shows the pendant type, and in the AVealdeu 

 Iguanodon, again, it is much more developed than in Trachodon, 

 of the Belly Eiver and Laramie Series. Comparing this fact with 

 the development of the teeth in these animals, we find that the more 

 complex development of the teeth runs parallel with the diminution 

 of the fourth trochanter. At the same time the diminution of the 

 fourth trochanter is also accompanied by the development of what 

 I formerly called the processus pectinealis of the Orthopode pelvis 

 (Foldtani Kozlony, 1899, Budapest), but for which I now adopt 

 the more appropriate name of processus pseudopectinealis. As it 

 is now possible to prove that the development of the processus 

 pseudopectinealis as well as the more complex structure of the 

 teeth are due to progressive and not to retrogressive evolution, and 

 since it is impossible to suppose that some sort of quite especial 

 chevauchement de specialisation is disturbing the whole line from 

 Hypsilophodon to Trachodon, it is equally impossible to sustain the 

 view that the smaller fourth trochanter represents the primary state, 

 and on account of this I think the fourth trochanter in Hypsilophodon 

 may be brought forward as one of the principal arguments for 

 sustaining my hypothesis concerning the fourth trochanter.' 



Conclusion. The following characters in Hypsilophodon can be 

 considered as new or definitely settled : — No sclerotic ring. Coro- 

 noidal process blunt and low. The dermal predentary certainly 

 edentulous. Prtemaxillary with rugosity on the front end. Con- 

 dylus basi-occipital, and the whole base of the skull very bird-like, 

 reminding us more of some Theropoda than of the true Ornithopodidae. 



1 Other arguments I intend discussing upon another occasion. 



