Zoology.] NATURAL HISTORY OF VICTORIA. [Fishes. 



Plate ]54. 



CYBIUM COMMERSONI (Lacep. sp.). 



Commeeson's Mackerel. 



[Genus CYBIUM (Cutier). (Sub-kingdom Vertebrata. Class Pisces. Order Acan- 

 thopterygii. Family Scomberidse.J 



Gen. CAar.— Body elongate, fusiform, moderately slender ; cleft of the- mouth wide 

 First dorsal long, with rather feebly developed spines, reaching nearly to the second dorsal ; 

 seven or more tinlets be'liind the dorsal ; anal fin resembling the second dorsal in size, shape, and 

 position, and with a similar number of tinlets behind it ; caudal iin moderate, forked, a strong 

 prominent keel on each side the base of tail. Greater portion of body naked, or with very small 

 scales, not forming distinct corselet. Teeth large, compressed, with cutting edges, lancet- 

 shaped, on edge of both jaws, small villiform teeth on the vomer and palatine bones, similar 

 patch on tongue. Seven branchiostegal rays. An air bladder. Indian and Atlantic Oceans.] 



D. 16 + D. 1 -H6 + X.; p. 24; V. 1 + 5 ; A. 1 + 16 + IX.; C|f ; L.l. 265. 



Description. — Height of the body at end of spinous dor.'^al 6| times in total 

 length, excluding- caudal. Length of the head five times in total length, excluding 

 caudal. Greatest depth of head rather more than three-fifths of its length. 

 Diameter of eye rather more than one-seventh the length of the head, nearer to the 

 snout than to hind edge of operculum. Profile of upper part of head nearly straight, 

 eloping, surface slightly convex and smooth. Snout pointed in front, lower jaw 

 less acute, but slightly longer, than the upper. Cleft of mouth extending to vertical 

 of hind edge of eye. Twenty-seven sub-equal, slightly irregular, triangular teeth 

 on each side in upper jaw, a little longer than wide. About 16, much larger and 

 longer, in lower jaw. A few rows of scales above the pectoral, behind the bead, 

 and along the base of the first and second dorsals. Pectoral fin narrow, falcate, 

 pointed, one-eighth the total length, excluding caudal. Ventral one-thiid the 

 length of the pectoral, of one spinous and five branched rays. First dorsal com- 

 mencing over base of pectoral, and extending to within a short space of the second 

 dorsal. Second dorsal twice as high as the first, falcate, little longer than high. 

 Anal nearly equal in size and shape to the second dorsal, its front edge a little in 

 front of verticar from middle of second dorsal. Ten finlets behind second dorsal, 

 and nine similar ones behind anal. Lobes of the caudal nearly equal, long and 

 narrow. Lateral line from bead slightly undulated to vertical from bind end of 

 second dorsal, suddenly descending from thence and re.^uming the longitudinal 

 direction from vertical of second finlet nearly in the middle of the body to the large 

 prominent median keel at base of tail ; two small curved ridges, one above and one 

 below median keel. Color: Upper part of back purplish-blue, fading into silvery- 

 white on lower part of sides and belly. The sides and belly marked with numerous 

 irregular, nearly vertical, stripes and spots of a dark brownish-purple. Anterior 

 dorsal purplish. Venti-als whitish. Pectoral, second dorsal, anal, and caudal fins 

 bluish-black with a brown tinge. Base of pectoral whitish. Lis golden-bronze. 



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