278 University Geological Survey of Kansas. 



transversely and slightly concave in the middle. Extending 

 downward and backward from near the anterior end of this 

 facet there is a ridge, which becomes very prominent just in 

 front of the condyle, and, continuing downward, forms a deep 

 groove with the posterior border, into which the anterior border 

 of the preoperculum is received to some extent. The anterior 

 portion of the bone is thin and continued forward quite a dis- 

 tance. The condyle for the operculum is long, narrow, and 

 situated about 45 mm. below the superior condyle. Just in 

 front of this condyle, externally, there is a large and deep pit, 

 which has another smaller one just above it. On the internal 

 side there is a prominent crest, which ends opposite the lower 

 end of the condyle just mentioned, and has another prominent 

 excavation in front of it. The lower end of the bone is some- 

 what bluntly pointed, but it does not seem to possess a facet at 

 this point, as is found in Saurodon. 



Hyomandibular : Length 265 ihm. 



Length of superior condyle 87 " 



Length of condyle for operculum 50 " 



Greatest width of bone (estimated) 160 " 



The ethmoid is much thickened and narrow in front, where 

 it forms a small beak, and broad and thin behind, w T here it 

 joins the frontals by a somewhat dentate suture. The bone is 

 moderately deep, and on the median line below there is a well- 

 marked median ridge, on either side of which there is a small 

 facet for the anterior condyle of the maxilla. In addition to 

 this there is also a small pit on each side, which probably 

 accommodates a part of the superior edge of the premaxilla. 

 The upper anterior portion is often covered with numerous 

 tubercles of bone, which fade out posteriorly. 



The frontals are broad, flat plates, and are the largest bones 

 entering into the formation of the top of the skull. Just back 

 of the ethmoid they join the prefrontals, and back of this form 

 the superior rims of the orbits. Posteriorly they unite with 

 the postfrontals, parietals, and supraoccipitals. The two 

 bones are united in the median line by a distinct suture, and 

 possess no characteristic markings other than an irregular 



