4 6o SCIENCE PROGRESS 



ceratopsian horn, the opinion is expressed that it is a weathered 

 ungual phalange of a member of the sauropod group. 



The earliest known Ceratopsia occur in the Judith River 

 beds, but of the ancestors of the latter we have no knowledge, 

 possibly for the reason that they were inhabitants of dry land, 

 instead of, like their successors, of swamps. The members of 

 the group living at the Laramie epoch exhibit advance over their 

 predecessors in the matter of size, the preponderance of the 

 supraorbital horns over the single nasal one, the fuller develop- 

 ment of the flange-like neck-shield of the skull, and the perfection 

 of a peculiar type of dentition. 



That the horned dinosaurs were herbivorous is manifest; 

 and it is suggested that while the edentulous, horny beak served 

 for cropping succulent leaves and shoots, the teeth in the sides 

 of the jaws chopped the food into short fragments. Swamps 

 were apparently the home of these dinosaurs ; and this may 

 negative the idea that they were exterminated by predaceous 

 mammals, since the latter have been supposed to be arboreal. 

 If, however, mammals are derived from theriodont reptiles, 

 the theory that the early forms were arboreal requires recon- 

 sideration. 



In connection with this group it should be added that to the 

 May number of the American Journal of Science Dr. Lull con- 

 tributed a paper on the head-muscles of dinosaurs, with special 

 relation to the origin of the neck-shield in the horned group. 

 Such evidence as can be obtained with regard to the cranial 

 musculature is gleaned from the form and proportions of the 

 skull, coupled with, in some cases, the marks of the attachments 

 of the muscles themselves. From the analogy of chamaeleons, 

 which, although insectivorous, masticate their food, it is inferred 

 that the horned dinosaurs had powerful temporal and feeble 

 pterygoid muscles, thereby differing from crocodiles, in which, 

 owing to the absence of mastication, the conditions in these 

 respects are reversed. It is pointed out that the neck-shield of 

 the Ceratopsia presents an analogy to the casque of the 

 chamaeleon-skull, both structures being a backward extension 

 of the parietal segment to afford space for the temporal muscles. 

 Owen's chamaeleon, from the Cameroons, presents a " mimicry " 

 of the Triceratops type in carrying three horns situated much as 

 in the dinosaur, although the horns are of dermal origin, and 

 devoid of bony cores. 



