CERATOPS MONTANUS. 



101 



Fig. 101.— Upper view of cranium of Meiolania 

 platyeeps Owen, drawn from a cast (No. 208) in 

 the U. S. National Museum. One-fourth nat- 

 ural size. 



The horn cores in the type specimen are subtriangular at base, but nearly round in section in the upper half. Their 

 position is represented approximately in the figures of the accompanying plate [shown here in fig. 100]. These horn cores 

 are slightly hollowed at the base, but are otherwise solid. The exterior texture and markings show that they were evidently 

 covered with true horns, and these must have formed large and powerful offensive weapons. In position and direction these 

 horn cores are somewhat similar to the large posterior pair of protuberances in Meiolania,"' one of the extinct Testudinata, 

 and to the corresponding ones of the existing Phrynosoma. The only known 

 example of similar structure in the Dinosauria is the single median horn core 

 on the nasals of Ceratosaurus, from the Jurassic. It is not improbable that 

 there were other horn cores on the skull in the present genus, but of this there 

 is at present no positive evidence. A detached median prominence resem- 

 bling a horn core was found with some similar remains, but may pertain to 

 an allied genus. 



The resemblance in form and position of the posterior horn cores to those 

 of some of the ungulate mammals is very striking, and, if detached, they 

 would naturally be referred to that group. 



The basioccipital found in place with these horn cores and represented 

 in PL XI [fig. 104, 1 b and 2 &,] is much elongated, and formed the entire 

 occipital condyle. Its exact position with reference to the horn cores could 

 not be determined. 



Teeth, vertebrae, and limb bones, which probably belonged to the pres- 

 ent genus, were all secured in the same horizon. They indicate a close affinity 

 with Stegosaurus, which was probably the Jurassic ancestor of Ceratops. 



Among other remains referred to the present reptile, but not found with the type specimen, are some peculiar large der- 

 mal plates, in pairs, that indicate a well-ossified armor. These plates show indications of being covered, in part, at least, 

 with scutes, as in turtles. Their position can not at present be determined. 



The type specimen on which the present genus and species are based was found in place, in the Laramie deposits of the 

 Cretaceous in Montana, by Mr. J. B. Hatcher, of the U. S. Geological Survey. Other specimens, apparently pertaining 

 to the same species, were secured in the same horizon of the same region. 



Remains of the same reptile, or one nearly allied, had previously been found in Colorado in deposits of about the same 

 age by Mr. G. H. Eldridge, also of the U. S. Geological Survey. 



The associated fossils found with the present specimens are remains of other dinosaurs, crocodiles, turtles, and fishes, 

 mostly of Cretaceous types. The mollusks in the same beds indicate fresh-water deposits. 



The fossils here described indicate a reptile of large size, 25 or 30 feet in length, and of massive proportions. With its 

 horned head and peculiar dermal armor, it must have presented in life a very strange appearance. 



The remains at present referred to this genus, while resembling Stegosaurus in various important characters, appear to 

 represent a distinct and highly specialized family that may be called the Ceratopsidae. They will be described more fully in 

 a later number of this journal. 



As is now well known, the above description is erroneous in many particulars. The beds 

 were not Laramie, but Judith River, a distinctly older formation. The horn cores in the Cer- 

 atopsidae are not firmly coossified with 

 the occipital crest, and they were not di- 

 rectly attached to either the parietals or 

 squamosals. Marsh's suggestion that 

 there were probably other horn cores on 

 the skull proved correct. The basiocci- 

 pital does not form the entire condyle, 

 but that element is made up of the coossi- 

 fied basioccipital and exoccipitals. The 

 large plates mentioned by Marsh as der- 

 mal plates are in reality squamosals. 

 The size of ' the animal indicated by the type material was considerably overestimated by 

 Marsh, and his suggestion that Stegosaurus was the Jurassic ancestor of Ceratops might at 

 present be questioned by many. 



a Meiolania platyeeps was described and figured by Sir Richard Owen in the Philosophical Transactions of the Royal Society, 1888, B, pp 

 181-191, pis. 31-37. Meiolania is a turtle, one of the Cryptodira, found on Lord Howes Island in the Pacific, and in at least two features is sug- 

 gestive of the Ceratopsia. The superior view of the hinder portion of the cranium here shown (fig. 101) exhibits, in addition to the low hind- 

 ermost pair of horns, "larger cores, which rise in advance of and exterior to these; the length of this core is 2 inches" (Owen). These cores 

 are the ones to which Marsh refers as being similar to those of Ceratops montanus, and, like those of the dinosaur, were evidently sheathed 

 with horn. Fig. 102 shows the osseous tail sheath of Meiolania, which also bears vascular markings similar to those borne on the 

 ceratopsian frill.— R. S. L. 



Fig. 102. — Side view of the coalesced terminal segments of the dermal bony 

 tail sheath of Meiolania platyeeps Owen, from a cast (No. 207) in the U. S. 

 National Museum. One-fourth natural size. 



