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KAMAKICHI KISHINOUYE: 



witb a well developed occipital crest. The bone is bounded in front by the 

 frontals, and laterally by the parietals, epiotics, and sometimes by the 

 exoccipitals as well. The posterior part of the bone gi-aduaUy converges, and lies 

 npou the median sntm'e of the epiotics. Tlie posterior slender jwrtion is often 

 extended over the sutm-e of the exoccipitals. This bone has httle characteristics 

 in different families. 



Tlic parietals are paired flat bones on both sides of the supraoccipital, and 

 rest on the sutural lines between the supraoccipital, sphenotics, epiotics and 

 sometimes pterotics, taking almost no part in the formation of the roof of the 

 brain cavity. The paiietals are surrounded in front by fi'ontals, on the outer side 

 by the pterotics, on the inner side by the supraoccipital, and behind by the 

 epiotics. The parietals are rather small, each with a high, longitudinal crest 

 on the dorsiil surface. The crest forms a part of the temporal crest, and is 

 a>utinuous to the crest on the frontals in front, and to the epiotic process 

 behind. In the Scombridae the parietals are provided with two crests. In the 

 Gybiidpe the parietals are generally separated from the pterotics. In the 

 Thunnidas also the parietals do not unite with the pterotics, at most some- 

 times touching with a corner above the sphenotics. In the Katsuwonidiie 

 the parietals are united to the ptarotics at the outer posterior side, and in 

 the genus Auxis the whole outer side of the former bone is bordei'ed by the 

 latter, as in this genus the sphenotics do not appear at the doisal surface of 

 the skull. 



The sphenotics form a part of the latsral wall of the optic lobe, and at 

 the Sixme time a part of the dorsal wall of the optic cavity, externally 

 they are a part of the aiiiculatiug facet for the anterior head of the 

 hyomandibular, moreover forming the pistorbital ridge. Tlie sphenotics are 

 bounded estcn'ually by the frontals, alisphenoids, prootics, pterotics, parietals, and 

 epiotics, and internally by frontiils, alisphenoids, prootics, supraoccipital, and 

 sometimes epiotics. In RastrelUger the piuietjils and pterotics are also found 

 round the sphenotics. The sphenotics are generally seen at the dorsal side of 

 the skull, between the pterotics and paiietals. In the Seombridai the sphenotics 

 are foimd at the dorsal, external side of the cranium, between the pterotic 

 crests. Tlie internal conca%-ity of these bones is sulxlivided by a septum. In 

 the Cybiidaj the sphenotics are more or le.ss flattaned bones and form a very 



