DAKOTA AND NEBRASKA. 34 



tal, parietal, and the squamosal, ending below in the post-auditory process. Between 

 the latter and the sessile occipital condyle a thick but slightly prominent mastoid 

 process and the rudimental paramastoid process are interposed. 



The basi-occipital and basi-spheuoid are co-ossified on a line with the posterior 

 surface of the glenoid cavities. 



The squamosal is nearly three times the length of its height. The suture formed 

 between it and the parietal proceeds in a nearly horizontal line from the lateral bor- 

 der of the inion to the top of the alisphenoid. - 



The co-ossified parietals are large, and cover in two-thirds of the top and sides of 

 the cranium. Together they are quadrate in outline, divergent postero-laterally and 

 convergent anteriorly. Their j)osterior border is concavely notched to join the supra- 

 occipital. In the median line the parietals are ten lines long, laterally thirteen lines. 



The fronto-parietal suture forms a transverse, zig-zag semicircle extending between 

 the summits of the aUsphenoids, and situated just posterior to the narrowest portion 

 of the cranium. 



The frontals remain sej^arated, and measure seven lines along the median suture. 

 The forehead occupies about half their length, and the post-orbital eminences ax'e 

 about their middle laterally. The angular j^rocesses are acuminate, and the notch 

 between them is four lines in depth by two and a third wide between their points. 



The fronto-maxillary suture curves backward and outward to the lachrymal bone, 

 the facial surface of which is a narrow triangle at the ant-orbital margin. 



The premaxillaries are as wide at the sides as they are high, and are not prolonged 

 at their upper extremity beyond the position of the canine teeth. 



The malar bone enters entirely into the constitution of the zygoma. About its 

 middle it forms a horizontal suture slanting between it and the end of the zygomatic 

 process. Its anterior extremity is deeply notched at the articulation with the 

 maxillary bone. 



Dentition. (Figures 25, 26, plate XXVI.) — As px-eviously mentioned, the teeth in 

 the fossil consist of two incisors, a canine, and seven molars on each side. The first 

 incisor of the left side and the second of the right, together with the third, fifth and 

 sixth molars of the same side, were lost in the recent condition of the animal, the 

 remaining sockets being filled with stone matrix. 



The incisors are small, and quite lateral in their position, being nearly in the same 

 line as the other teeth. They are separated from each other and the canine by short 

 intervals, and the anterior pair of the two sides are a line and a quarter apart. 



One of the remaining incisors, the second of the left side, has lost its crown. The 

 first incisor of the right side has the crown l^roken ; the portion preserved is com- 



