Nos. IAND2.] AX ATOMY OF SCOMBER SCOMBER. 103 



vertebral depression in the hind end of the bone, reaching- that 

 surface sHghtly dorso-posterior to the bottom of the depression. 

 This line was not examined microscopically. Macroscopically it 

 has the same general appearance as the lines that form the axes 

 of the vertebrae and connect the depressions on their opposite faces. 

 It seems to indicate that the anterior end of the chorda here turned 

 upward, or was pushed upward, above the hind end of the eye- 

 muscle canal ; and the canal or pit in the basioccipital looks as if it 

 might be the remnant of the anterior, conical depression of a ver- 

 tebral body, the posterior depression of which was represented in 

 the depression on the hind end of the basioccipital. 



The basioccipital supports, on each side of its dorsal surface, 

 the occipitale laterale of the corresponding side of the head. The 

 anterior part of the latter bone, on each side, rests upon the thin 

 ridge that forms the lateral boundary of the saccular groove. Its 

 posterior portion rests upon an inclined surface on the dorsal sur- 

 face of the basioccipital, and the lower, lateral edge of this little 

 surface projects as a slight process or ridge on the lateral surface 

 of the solid, vertebra-like hind end of the bone. The little surface 

 looks dorsally, anteriorly and laterally, and between the two sur- 

 faces of opposite sides of the head there is a small, flattened, 

 median surface, which forms the floor of the foramen magnum. 

 The posterior part of this median surface is wide. The anterior 

 part may be reduced to a narrow line or even entirely disappear, 

 the two occipitalia lateralia then here covering the entire dorsal 

 surface of the basioccipital. 



At the extreme postero-ventral end of the lateral surface of the 

 basioccipital there is a slight, but well-marked depression which 

 marks the surface of origin of a ligament that runs outward and 

 backward and is inserted on the inner surface of the supra- 

 clavicular. 



The Occipitale Laterale (OL) adjoins the petrosal ante- 

 riorly, the squamosal dorso-antero-laterally, and the exoccipitale 

 dorsally. The dorsal part of its lateral surface is covered by the 

 intercalar. The dorsal part of its mesial edge adjoins its fellow 

 of the opposite side of the head, the adjoining edges of the two 

 bones being covered externally by the lower end of the postero- 

 inferior portion of the supraoccipital. The edge of the bone is 



