COMPARATIVE STUDY OF SCOMBROID FISHES. 
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muscle is rather narrow, and meets the axial skeleton with a narrow neck or 
root in the hypaxial portion only. 
Ligament in a deep median groove between the anterior end of the 
frontals is attached to the skin, anterior to the median foramen of the skull. 
This ligament is a characteristic of this family. 
The transverse process of some precandal vertebrae is broad, well developed. 
The first vertebra is greatly reduced in height and firmly anchylosed to the 
skull. Inferior foramen is small, and is found in the caudal vertebrae only. 
Number of vertebrae is constant, 39 in total, of which 18 are precaudal, and 
21 caudal. The haemal canal is closed in the tenth or eleventh vertebra, i. e. near 
the middle ,of the precaudal region. Alisphenoids meet at the ventral median 
line. Anterior precaudal vertebrae, are broader than high. Hoof of the mouth 
cavity is covered with numerous plates covered with villous teeth. 
Many systematists put too much weight on the length of the pectorals, 
but it has little value in the classification. 
Key to the genera of Thunnidae. 
Cutaneous blood-vessels pass through the myotome of the fifth vertebra, surface 
of the liver striated with fine venules. Thunnus. 
Cutaneous blood-vessels pass through the myotome of the seventh vertebra, 
surface of the liver not finely striated with venules. 
Posterior cardinal vein is not continuous with the Cuvierian ducts. 
Vascular plexus on the inner side of the liver. Parathunnus. 
Posterior cardinal vein is continuous with the Cuvierian ducts, vascular 
plexus in the haemal canal. Neothunnus. 
Genus Thunnus South. 
Thunnus South, 1845. 
Thynnus, Cuvier, 1817 ; Günther, 1860. 
Orcynus, Cuvier, 1817. 
Germo, Jordan, 1888. 
Albacora, Jordan, 1889. 
Body plump, robust. The first haemal canal is closed in the tenth vertebra. 
Anterior haemal arches of the precaudal region are turned forward and narrow. 
Bight side of the stomach receives an artery from the downward branch 
of the coeliaco-mesenteric artery. Two large branches of the coehaco-mesenteric 
artery send their blood to the liver, and they are finely divided into plexus 
on the inner side of the liver. These plexus reunite into several arteries to 
