Nos. IAND2.] ANATOMY OF SCOMBER SCOMBER. 99 



short, flat process which projects laterally and backward, its flat 

 surface being presented upward and slightly backward. This flat 

 surface is continued forward and mesially along the dorsal surface 

 of the bone, close to its dorso-posterior edge, and extends be- 

 yond the exoccipitale on to the adjoining portion of the supra- 

 occipital. It gives support to the long, antero-mesial process of 

 the suprascapular, that process having a sliding motion upon it. 

 At about the middle of the hind edge of this flat surface there is, 

 on the exoccipitale, a slight, irregular eminence which gives origin 

 to a short round ligament which is inserted on the under surface 

 of the suprascapular. Beginning at the base of the short, flat, 

 posterior process above described, and continuous with it, a thin, 

 laminar process, or ridge, runs forward and slightly mesially along 

 the dorso-lateral edge of the exoccipitale, and slightly overlaps, 

 laterally, the corresponding ridge on the dorsal surface of the 

 parietal. It projects dorso-laterally and forms the hind end of 

 the ridge that separates the temporal and supratemporal grooves. 



The lateral face of the exoccipitale forms the mesial wall of 

 the posterior portion of the temporal groove, and is deeply hol- 

 lowed out by that groove. The posterior face of the bone, has, 

 on its mesial half, a depressed region, which is often sharply 

 marked off from the rest of the bone by a rounded edge, or slight 

 ridge, which runs upward, forward and slightly laterally. 



The internal surface of the bone is concave. On the internal 

 portion of its inferior edge there is a semicircular indenta- 

 tion which forms the dorsal half of the circular opening of 

 a recess of the cranial cavity. This recess is directed backward 

 and laterally, is greatly enlarged at its distal end, and there lies 

 between the thick, inferior edge of the exoccipitale, and the ad- 

 joining part of the occipitale laterale. The recess lodges the hind 

 end of the sinus utriculi posterior, and from its enlarged distal 

 end the external and posterior semicircular canals take their 

 origins. The external canal runs laterally, forward and slightly 

 upward, passing at once into the canal already described in the 

 squamosal. The posterior canal runs upward and mesially, and 

 then forward, in the exoccipitale, and reenters the cranial cavity 

 by a large opening near the dorsal edge of the cerebral surface of 

 the exoccipitale. A groove on the cerebral surface of the skull, 



