p6 ALUS. [Vol. XVIII. 



The squamosal consists, as already stated in an earlier work 

 (No. 9), of two parts, an inferior portion, or body, and a superior 

 portion which has the appearance of being a large, plate-like 

 piece of bone applied to the dorsal surface of the body of the bone. 



The body of the bone is thick and stout, and its edges are 

 everywhere separated from the adjoining primary ossifications 

 of the skull by Hues of cartilage or tissue, excepting only where 

 it is overlapped externally by the spHnt-like processes of the 

 petrosal. It lies in an inclined position, inclining upward and 

 laterally, approximately at 30° to a horizontal plane, and it may be 

 said to have four exposed surfaces ; one presented ventro-laterally, 

 one dorso-laterally, one dorso-mesially and one posteriorly. The 

 ventro-lateral surface forms the dorso-posterior portion of the 

 side wall of the skull ; the dorso-lateral surface forms a small 

 part of the floor of the dilatator groove and bears on its mesial 

 edge the superior, laminar portion of the bone; the dorso-mesial 

 surface forms the lateral and larger portion of the posterior, de- 

 pressed portion of the temporal groove ; and the posterior surface, 

 or hind end of the bone, forms the dorso-lateral part of the hind 

 end of the skull. From its hind edge a long, thin, triangular proc- 

 ess projects backward and laterally, its sharp, pointed, outer end 

 forming the extreme dorso-lateral point or corner of the hind end 

 of the skull. 



The superior, laminar portion of the squamosal is a broad, flat 

 piece of bone which has the appearance of being applied, some- 

 what crosswise, by the posterior half of its ventral edge, to the 

 anterior half of the mesial portion of the dorso-lateral surface of 

 the body of the bone. The plane in which the piece or process 

 lies is directed forward and mesially, and it inclines upward and 

 laterally at a considerable angle to the plane of the body of the 

 bone. The process forms the posterior portion of the ridge that 

 separates the temporal and dilatator grooves, and its anterior half 

 projects horizontally, forward, and mesially beyond the anterior 

 end of the body of the squamosal. The inferior edge of this pro- 

 jecting, anterior portion of the process is flattened, and the small 

 ventral surface so formed rests upon the dorsal surface of the 

 postorbital ossification, immediately mesial to the slight groove 

 on that surface that forms the postero-mesial, depressed portion 



