COMPARATIVE STUDY OF SCOMBROID FISHES. 
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end, its upper surface flattened and naked, but the opercles are scaly. Caudal 
peduncle rounded in cross-section, having no lateral keel. A pair of small keels 
are found on each side of the tail. Lateral line gently curved, wanting mark¬ 
ed bendings or undulations. Adipose eyelids present. Scales cycloid, often 
finely crenulatecl or more or less ctenoid at the posterior margin. Corselet in¬ 
distinct. The scales at the pectoral region have the same structure as those in 
the remaining regions, but the former are only a little larger than the latter. 
The former are not covered with a connective tissue membrane. Postorbital 
scales rather large, unequal in size. In the ventral half of the body, rows of 
scales run nearly parallel to the ventral median line of the caudal region. 
Mouth large with minute teeth. Tongue very small and smooth. The 
maxillary is almost entirely covered by the preorbital, and the supplementary 
bone at the posterior end is very small, slender and insignificant. Premaxillaries 
are very slender and weak. Gill-rakers very numerous, long, slender and much 
compressed, with two rows of fine diverging pairs of long denticles on the inner 
side. Gill-lamellae very short at the angle of gill-arches. Branchiostegal mem¬ 
branes very broad and overlapping each other at the symphysis. 
Opercle short, and notched at the posterior margin. Subopercle very narrow. 
Preopercle comparatively large, rounded and expanded at the lower posterior 
corner. Clavicular ligament is inserted at the posterior end of the exoccipital. 
Fins not well developed. Interspinous bones are weak and slender. Fin-rays 
are transversely articulated. The second dorsal is lower than the first and the 
two dorsals are distinctly separated from each other. The first spine of the first 
dorsal is shorter than some succeeding spines. The second dorsal and the anal 
are covered with small elongated scales. 
The abdominal cavity is ellipsoid in cross-section, with the longer diameter 
vertical. Peritoneum generally black. Pylorus ascending. Pyloric coeca nu¬ 
merous, arranged in many longitudinal rows. They are rather large, opening 
directly to the duodenum, and are loosely connected with connective tissue 
fibres. Alimentary canal long and folded. The liver is a small triangular 
mass, occupying the left anterior corner of the abdomnial cavity. Kidneys thin, 
elongated and divided into two before the pharyngeal muscle, which is inserted 
into the third or fourth vertebra, or into both. 
Skeleton thin, but firm. Skull elongated and the greater part of the fron- 
