JSTo. 5.1 SHUFELDT ON THE OSTEOLOGY OF EREMOPHILA. 123 



The superior mandible is rather broad at its base 5 the culmen, origi- 

 nating in a flattened space just anterior to the fronto-mandibular artic- 

 ulation, is rounded throughout its extent and gently curved downwards, 

 while below, the line joining the middle points of the bases of the triangles- 

 above mentioned, averages 7 millimetres in length. The sides of the in- 

 ter-maxillary are smooth,presenting only occasionally a row of very mi- 

 nute foramina for examination ; sometimes a faint suture shows itself on 

 either side, extending almost down to the nostril, between this bone and 

 each nasal. Beneath, the palatine fissure is broad and rounded ante- 

 riorly, the roof of the mouth beyond being gently concave and grooved 

 mesially for its entire length, and marked by a few foramina. The ex- 

 ternal apertures of the nostrils are quite large, nearly elliptical in out- 

 line, approaching each other within less than .5 of a millimetre above. 

 Their borders, formed by the nasals behind, are sharp ; anterior, more 

 rounded. The major axes of these openings average 4 millimetres, 

 the corresponding minor axes 3 millimetres. The planes passed through 

 their peripheries look upward, outward, and forward. The nasals are 

 fan-shaped, both above and below, the expansion being slightly twisted, 

 in order to accommodate themselves to the form of the bill. The broad 

 lachrymals, assisted by the prefrontal, effectually separate the orbital 

 vacuities from the rhinal chambers. The latter are remarkably open, 

 owing to the size in the skull of the various apertures leading into 

 them from without, already described, and devoid of all septa or bony 

 offshoots, although the prefrontal, intermaxillary, and palatines together 

 occasionally develop irregularly formed ethmo-turbinals, that extend into 

 this space from behind and afford the necessary surface for the pitui- 

 tary membrane. But there is nothing that has the slightest semblance 

 to an osseus septum narium. The anterior olfactory foramina, narrow 

 slits one millimetre long, are found between the lachrymals and pre- 

 frontal, close to the vertical septum of the latter ; their outer extremi- 

 ties being the superior, they are seen to look downward and forward 

 as thej' open into the nasal cavities from the bases of the concavities 

 formed by the bones above mentioned. 



The orbital cavities are capacious, having rather a forward look ; at 

 the same time they look a little downward. Their limiting borders are 

 ovate in outline, with the greater end backward, being incomi^lete be- 

 low. Anteriorly the septum that divides them is remarkably entire and 

 of considerable thickness 5 posteriorly and above there exists quite a 

 deficiency, of a shape shown in PI. LY, Fig. 22; this is situated just in 

 front of the large quadrilateral rhinencephalic foramen, and allows a good 

 passage from either orbit into the brain-case. The same condition ob- 

 tains below with the opening for the exit of the optic nerves, only the 

 latter is much smaller and quite circular ; to its outer side there are 

 several minute foramina that lead directly into the brain-ca«e. The 

 groove for the first pair is distinct anteriorly on cither side, and opens- 

 into slits between the prefrontal and lachrymals, similar to those described 



