100 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.55. 



Principal Measurements of the Type-Specimen. 



mm. 

 Greatest length of dentary G70 



Greatest depth of dentary 229 



Length of dental series 535 



Breadth of nasals at base of horn core 140 



Distance from top of nasal horn core to inferior surface of 



nasals 75 



I have been unable to find in the collections of the U. S. National Museum 



the squamosal mentioned by Marsh as pertaining to the type, and can say 



nothing concerning the form of this important element. The other portions 

 of the skeleton preserved show no peculiarities vporthy of note. 



The missing squamosal mentioned by Hatcher was found in one 

 of the recently opened boxes. The left squamosal, lacking the pos- 

 terior end (see pi. 4) , was attached to the skull. Although Hatcher 

 collected this specimen, the presence of nearly the entire skull had 

 obviously entirely escaped his memory, as no allusion is made to it 

 in any of his writings. The characters pointed out by Hatcher for 

 distinguidiing this species are for the most part of a trivial nature 

 and little dependence can be placed on them as representing con- 

 stant specific differences. The peculiarities found in the dentaries 

 may be attributed in a great degree to the severe crushing whicli 

 these bones have undergone, in addition to the malformations in the 

 left element to which Hatcher calls attention. A comparison of the 

 dentaries with others in the collection of the United States National 

 Museum fails to disclose any great degree of difference in the for- 

 ward extension of the mandibular fossa, its apparent extension 

 being due to the absence of the overlying splenial and to deforma- 

 tion of the bone by vertical pressure. The width of the nasals also 

 appears to have been exaggerated by crushing. Of the specific 

 characters pointed out by Hatcher, the reduced nasal horn core 

 alone is probably valid, though it may be only a sex character. 

 The supraorbital horns as compared with the types of T. calicomis 

 Marsh and T. elatus Marsh are somewhat shorter and lack the great 

 forward curvature. They are not quite as stocky as those of T. 

 hrevicornus., which they resemble most nearly in a lateral view. 



After a careful comparison of this additional material of T. ohtusus 

 with the several types in the United States National Museum collec- 

 tions, and with the figures and descriptions of other species of the 

 genus preserved elsewhere, I am unable to detect characters that 

 would satisfactorily distinguish this species. 



In the present accepted classification of the Ceratopsia, and es- 

 pecially of the species of the genus Triceratojys^ great importance is 

 attached to the development of the nasal and supraorbital horn 

 cores, and the peripheral outgrowths of the frill. It is not yet clear 

 how much dependence can be placed on the differences found in these 

 horns, or their almost complete absence as in T. obtiistis. There is 



