DAKOTA AND NEBRASKA. 347 



about the same proportions as in the European Hedgehog. The zygoma is relatively 

 about as strong as in the latter, and is arched to nearly the same degree. It has no 

 upward rise in its course forward, but inclines downward from its posterior root to its 

 junction with the face. It possesses no post-orbital process. 



A moderately deep fossa occupies a position both in front and belxind the zygo- 

 matic arch. The anterior fossa impresses the maxillary just in advance of the malar 

 bone, and beneath the orliit. The posterior fossa impresses the squamosal over the 

 auditory archway, and extends from upon the back of the zygoma to the border of 

 the inion. 



A foramen occupies the bottom of the posterior fossa of the zygoma, and three 

 others pierce the squamosal just above the fossa. 



The orlDital space is defined from the temporal fossa only by the smooth convex 

 post-orbital eminence. A small foramen pierces the summit of the latter. 



The ant-orbital margin from the position of the lachrymal bone is acute, and curves 

 downward and backward upon the zygoma. Its most anterior part is above the posi- 

 tion of the antepenultimate molar. 



The iufra-orl)ital foramen is situated a short distance in advance of the orbit, 

 above the interval of the fourth and fifth molars. It is oval, nearly as wide as high, 

 and about a line in diameter. 



Posterior view. — The inion presents a wide, horizontal summit, emai-ginate at the 

 middle. The sides are convex, and end below in the post-auditory processes of the 

 temporals. 



A prominent median ridge descends fi'om the upper border of the inion, and ex- 

 pands above the occipital foramen. The lateral surfaces are depressed, and are most 

 prominent aj^proaching the latter. A deeper depression on each side is formed upon 

 the pars mastoidea of the temporal. 



Tlie occipital foramen is sub-pyriform, three and three-quarter lines high and four 

 and a quarter lines wide. The occipital condyles are comparatively but moderately 

 prominent, and are quite sessile. They project more interiorly than posteriorly. 



Inferior view. (Figure 26, plate XXVI.) — The basi-occipital is of moderate width, 

 and but feebly cai-inated. It rapidly narrows to the conjunction of the basi-sphenoid, 

 which is slightly ascending. The articulation of the two is the most pi'ominent por- 

 tion of the basilar surface. 



The paramastoid process is rudimental, and the mastoid process is but little better 

 developed. The contiguous post-auditory process of the squamosal is better devel- 

 oped than either of the former. 



The auditory bulla on one side is broken away, but upon the other appears to be 

 entire and of remarkable form. It is comparatively small, and is in the form of a 



