THE HORNED DINOSAURS GILMORE. 383 



The frill and horn cores of most of these animals were in life un- 

 doubtedly invested in a close-fitting covering- of horny skin, as im- 

 plied by the deep ramifying system of depressed channels on their 

 outer surfaces for the transmission of blood vessels. The character 

 of this covering was probably like that found on the horns of the 

 honied toads, as shown in plate 6, figure on right, where the right- 

 hand spike of the central pair has its outer horny covering still in 

 place. It will also be observed that this sheath slightly increases the 

 length of that horn as compared with its fellow of the opposite side, 

 and it is presumed that the horn cores of the Ceratopsia would be 

 similarly lengthened. Professor Lull 1 has observed on a young 

 specimen in the Yale Museum " a layer of black powdery substance, 

 a half inch in thickness, doubtless the carbonized remains of the 

 actual horn, surrounding the base of the horn-core.' , 



All of these animals were quadrupedal with short massive limbs, 

 and broad elephantine feet that doubtless had the toes tipped with 

 hoofs, a short, rounded, but broad-barreled body, with a short neck 

 that was completely covered by the projecting frill of the skull. The 

 tail for a dinosaur was comparatively short, though in life it prob- 

 ably dragged upon the ground. 



The teeth form a single cutting row in each jaw, the lower closing 

 inside the upper so that the wear is on a vertical plane, and in the 

 process of opening and closing the mouth thej' act like the opposing 

 blades of a pair of shears, the teeth functioning as the cutting organs. 

 Their structure and arrangement indicate that these animals fed on 

 herbage, probably the stems, branches, leaves, and twigs of shrubs 

 and trees. This food gathered up by the efficient cropping beak, was 

 passed back to the teeth there to be reduced into smaller bits and 

 made suitable for reception into the stomach. 



The eyes were set in deep thick-rimmed sockets, which look directly 

 outward, thus evidently limiting the forward range of vision, but 

 affording ample protection to these highly sensitive but necessary 

 organs. It is now known from the completely preserved skeleton 

 of Monoclonius (see pi. 2), that the eyeball was still further pro- 

 tected by a ring of bony sclerotic plates. 



Although having such immense heads the brain is smaller in pro- 

 portion to it than in any known vertebrate animal, being but little 

 larger than a man's fist. The small size of this organ is graphically 

 depicted in the accompanying illustration of a skull sectioned 

 through the center of the brain cavity. (See pi. 3, lower figure.) 



The preservation of anything that pertains to the soft anatomy 

 of the horned dinosaurs was little expected, and yet within the 

 past few years specimens have been discovered having considerable 



1 Proc. Seventh Internal;. Zool. Cong., Boston, 190T, 1910, p. 3. 



