766 PROFESSOR TURNER ON ZIPHIUS CAVIROSTRIS 



The occipital surface of the skull, broadly triangular, ascended almost ver- 

 tically to near the summit of the cranium, where it articulated with the frontal. 

 The foramen magnum, directed backwards, was of almost equal diameter (about 

 2\ inches) vertically and transversely. The occipital condyles were inclined 

 obliquely downwards and forwards at the sides of the lower half of the foramen, 

 but did not coalesce. Their faces were smooth, convex, and directed back- 

 wards and outwards. A vertical, but not quite mesial, ridge ascended from the 

 foramen to the summit of the supra-occipital. No trace of an interparietal 

 bone was seen. The ex-occipital, broad and thick, was prolonged at its outer 

 and lower part into a thick process (par-occipital or jugal), which was separated 

 by a deep cleft from the lateral elevation of the basi-occipital. 



The temporal was an irregular bone, situated in front of the ex-occipital 

 with which it articulated. The part, jointed with the jugal process of the latter, 

 had not only the shape of a mastoid process, but was articulated with the 

 squamous temporal by a strongly denticulated suture. A strong zygomatic pro- 

 cess arched forwards, and almost touched the post-orbital process of the frontal. 

 A thinner, more scale-like portion of the temporal ascended to form a part of the 

 floor of the temporal fossa, where it articulated with the parietal. The under 

 surface of the temporal bone presented two concavities : an antero-external, or 

 glenoid, for articulation with the lower jaw, and a postero-internal, for the lodg- 

 ment of the petro-tympanic bone. 



The recess for the lodgment of the petro-tympanic bone was of small size, 

 and bounded by the basi and ex-occipitals, and by the squamous and mastoid 

 parts of the temporal. The petrous bone was not anchylosed to the tympanic ; 

 it was 2^ inches long by 1^ inch in its greatest transverse diameter, though its 

 outline was irregular. Externally it passed for some distance behind the mas- 

 toid, with which it articulated by a smooth flattened surface, whilst its inner end 

 was in apposition with a smooth, almost vertical process of the squamosal, 1^ 

 inch in length. The canal in the bone for the auditory nerve was relatively 

 small. The surface of the bone, forming the inner wall of the tympanum, had 

 the solid, rod-like stapes articulated by a movable joint with the foramen 

 ovale ; the incus and malleus had not been preserved. Opening into the recess 

 in which the petrous bone was lodged, was a circumscribed canal, communi- 

 cating with a cranial cavity obviously for the transmission of the seventh nerve. 

 Between the ex- and basi-occipital were two canals, apparently for the trans- 

 mission of the eighth and ninth nerves. Somewhat in front of, and internal to 

 the base of the vertical process of the squamous, was another canal situated in 

 the ali-sphenoid, which had probably transmitted the inferior maxillary division 

 of the fifth nerve. 



The tympanic bone, 2f inches in length by If inch in greatest transverse 

 diameter, possessed the conchoidal form so characteristic of this bone in the 



