COMPARATIVE STUDY OF SCOMBROID FISHES. 
311 
ou the dorsal, posterior part we find five longitudinal ridges or crests. Tire 
median ridge is continuous to the occipital crest, separating the right and 
left lateral muscles, and affording the surface of insertion to the protractor 
dorsalis at the posterior part. The inner ridge or temporal crest of Starks 
and cretes intermediäres of Cuvier are found at the mid-dorsal bend of the 
epaxial part of the lateral muscle, while the outer ridges or pterotic crests 
separate the lateral muscle from the facial muscles. 
In the Scombridæ the skull (fig. 30, a, b) is comparatively high, being 
nearly as high as broad, and is gradually pointed towards the anterior end. 
The lateral ridges on the dorsal sides of the skull converge forward, and 
disappear near the posterior margin of the frontal s. Moreover there is a pair 
of short, accessory crests on the external side of the temporal crests. The 
pterotic processes are stout, sharply pointed and nonflexible. The temporal 
and pterotic crests are separated by a deep furrow and are connected at the 
posterior end with a nearly vertical ridge. Nearly the anterior half of the 
skull is directly under the skin, and is not covered by the lateral muscle. 
Fig. A. Median sagittal section of the skull. 1, Scomber japonicus ; 2, Oybium niphonium ; 3, 
Thunnus orlentalis ; 4, Kalsuwonus pelamis. The first vertebra is anohylosed to the skull of 
Thunnus. 
