420 



MEMOIRS OF THE CARNEGIE MUSEUM. 



LXVI, Fig. 1 and text fig. 11a.) From this material combined we are now in pos- 

 session of practically all the anatomy of the skull of D. annectens. With the 

 exception of the ends of the nasals, the anterior portion of the left horn, and the 

 points of the premaxillaries this specimen is quite complete. The skull is somewhat 

 depressed, so that the region about the horns and anterior portion of the maxil- 

 laries appears broader than in the New Haven specimen described above; however, 

 the present specimen is in reality more robust. In proportion the horn-cores 

 of D. annectens from the John Day are considerably heavier than in the later Ne- 

 braskan species and the tips of the nasals were evidently quite long. The constric- 



FiG. llfl. Diceratherium annectens (Marsh). No. 7.324, Cope Collection, American Museum of Natural 



History. Hypotype. X {. 



tion between the orbit and the nasal horn is, as in D. armatum, much shorter and 

 sharper than in D. niobrarense or D. cooki, and the occiput extends further back of 

 the posterior angle of the zygomatic arch and overhangs the occipital condyles 

 to a greater degree. There is also a well-defined and quite heavy sagittal crest. 

 The supratemporal ridges are distinct, but more gently oblique or more gradually 

 converging towards the sagittal crest than in the Nebraskan species, which is 

 due to the smaller brain-case in the form from the John Day. The occiput is 

 somewhat more elevated above the occipital condyles and the transverse diameter 

 of the occipital plate is actually less, though the skull is larger than that of the 

 average skulls of D. cooki found in the Nebraskan quarries. As stated, the pre- 

 maxillaries are broken off anteriorly, but it is very evident that the diastema from 

 the cheek-teeth to the upper incisor in this specimen was as long as in the type 

 at New Haven. The pre-orbital foramen is located above the anterior, or rather 

 the middle, region of P'' as in D. cooki, but it is further back of the narial border, 



