FISHES—SCOMBRIDAE-TRACHURUS SYMMETRICUS. 
107 
at its onset than further hack. The caudal keel or ridge begins almost evenly with the ante¬ 
penultimate finlets, and extends to the base of the caudal fin, being more developed upon its 
middle than at its extremities. The accessory keels at the base of the caudal fin may easily he 
observed, although much less developed than the one just referred to. 
The upper surface of the head, and occipital region to the first dorsal are bluish black. The 
dorsal region is rather lighter, though bluish still, with three longitudinal and somewhat 
oblique blackish streaks, starting from various points on the lateral line and running towards 
the dorsal line, parallel to one another. The rest of the flanks and sides of the head are silvery, 
whilst the abdominal region, properly so called, is yellowish golden. The dorsal and caudal 
fins are bluish black also, the anterior dorsal being a good deal darker than the others ; the 
pectorals are greyish above and yellowish beneath, whilst the ventrals and the anal are of a 
pure lemon hue. 
List of specimens. 
Catal. 
No. of 
Sex and 
Locality. 
When collected. 
Whence obtained. 
Nature of specimens. 
No. 
spec. 
age. 
688 
1 
Adult.. 
San Diego, Cal_ 
1857 
A. Cassidy___ 
Alcoholic_- 
TRACHURUS, Rafin. 
Gen. Char. —Body elongated, compressed, sub-fusiform in its profile. Head well developed, compressed also. Mouth 
moderate ; lower jaw longest. Small teeth on the jaws ; velvet-like teeth upon the vomer and palatine bones. Opercular 
apparatus smooth. Branchial apertures continuous under the throat. Two dorsal fins distinct. Two free spines in advance of 
the anal fin. Caudal furcated. Scales moderate in size. Lateral line composed of narrow and vertical scutellae, keeled 
upon their middle and acerated posteriorly. 
Syn. — Trachurus, Rafin. Caratt nuovi Generi e nuove specie di Animali, &c. della Sicilia, &c. 1810.—Cuv. & Val. Hist, 
nat. des Poiss. IX, 1836, 6. 
Observ. —This genus may he distinguished from Caranx proper by the structure of its lateral 
line, which is composed of vertical, scale-like scutellae throughout its whole length, whilst in 
Caranx the same scutellae are observed upon the posterior portion of the body only. The 
general shape of Trachurus appears to he more elongated also than in Caranx. In both, 
however, we observe a small, nearly horizontal spine, at the anterior margin of the first dorsal 
and directed forwards. 
1. TRACHURUS SYMMETRICUS, Grd. 
Spec. Char. —Head forming the fourth of the total length. Posterior extremity of maxillary extending to the anterior rim 
of the orbit. Scutellae of lateral line smallest upon ils bent, under the anterior third of the second dorsal. “ Greenish brown 
above, lighter on the sides, silvery beneath. Sides silvery. A brownish black blotch at the superior and posterior angle of the 
opercle. Dorsals somewhat clouded ; other fins nearly colorless.” 
Syn. —Caranx symmetricus, Ayres, in Proc. Cal. Acad. Nat. Sc. I, 1855, 62. 
The specimen which we describe is hut five inches and a quarter in total length, whilst the 
one first observed by Dr. Ayres measured seventeen inches, and since we have to deal with an 
immature specimen we will briefly state a few of its most prominent features. 
The body is compressed and sub-fusiform in its profile, the head forming about the fourth of 
