Zoology.'] NATURAL HISTORY OF VICTORIA. {Fishes. 



Plate 125. 



MONACANTHUS HIPPOCREPIS (Quoy and Gaim. sp.). 

 The' Horse-shoe-marked Leather- jacket. 



[Genus MONACANTHUS (Ccv.) + ALUTERIUS (Cuv.). (Sub-kingd. Vertebrate. 

 Class Pisces. Sub-class Teleostei. Order Plectognathi. Fam. Sclerodermi.) 



Gen. Char. — Body compressed, elevated in tbe middle. Scales small, rbombic, distinct on 

 inner surface of skin, obscured by minute spines rougbening the outer surface ; sides of tail 

 with 4 or 6 hooked spines in 2 or 3 rows, smaller or absent in females. Lateral line absent or 

 indistinct. Teeth : 6 broad, flat, sharp-edged incisors in outer row of each jaw, and 4, forming 

 an inner row, in upper jaw, alternating, one between the 1st and 2nd, and the other between the 

 2nd and 3rd, on each side of the outer row. Fins : First dojsal composed of one large, thick, 

 rough, bony spine, which may be fixed in erect position or lowered into a pit on back, over the 

 eye ; membrane very small, triangular at base, with or without a second small, rudimentary 

 spine. Soft dorsal and anal long and low, with simple unbranched rays. Pectoral small, 

 rounded. Caudal rounded. Ventrals replaced by a small spine, sometimes rudimentary or 

 absent. Branchial slit in front of base of pectoral. No barbel to chin. Tropical and sub- 

 tropical seas.] 



Description. — Body sub-fusiform, compressed, profile nearly straight, rising- at 

 an angle of about 30° from the longitudinal lateral midline to a little behind first 

 dorsal, thence slightly concave to origin of second dorsal, the dorsal line beyond this 

 being- nearly straight to the base of the caudal. Greatest depth of body about one- 

 third of the length, including- the caudal fin. Eye larg-e, close to the frontal level. 

 Branchial slit oblique, nearly twice the length of the diameter of the eye ; lower end 

 a little below middle of base of pectoral. First dorsal spine straight, irregular, 

 slig-htly less than half the length from its base to the snout, placed over the posterior 

 third of the eye ; section convex in front, angular, nearly flat behind ; lateral edges 

 with a row of about 20 very small spines, irregular in size, shape, and direction, 

 some extending upwards, others downwards and outwards ; anterior face covered 

 with minute, rounded granules having a tendency to run into flexuous longitudinal 

 lines, the two middle anterior rows much larger than the others, slightly spinose in 

 some specimens towards the apex; second ray absent in most specimens. Ventral 

 spine at end of pelvic ridge scarcely perceptible, covered with a very small, spinu- 

 lose, oblong plate. Pectoral broad, rounded, of 13 rays. Second dorsal low, rising 

 rapidly to the fifth ray, thence continuing with little diminution to near the end, of 

 35 simple rays. Anal about as high as the second dorsal, the first ray shorter than 

 the succeeding ones, which diminish slightly till near the end, of 32 or 33 simple 

 rays. Caudal fin sub-truncate, slightly convex, of 12 thick, doubly-branched rays, 

 set with small spinulose granules. Skin with small rhombic scales, with fine 

 granules, and a line of from 3 to 7 larger, thicker, sharp-pointed spines, inclined 

 backwards on each ; 4 very much larger, conical spines on each side of the base 

 of the tail, inclining backwards in female, forwards in male. Color : Head, 

 cheeks, and portion of back yellowish-olive, darkest on sides of head; belly 

 lighter olive as far as anal fin ; from tip of pectoral to about end of anal fin a 

 broad, deep chrome-yellow, ovate patch, having a black horse-shoe-shaped mark 

 Vol. II.— Decade XIII.— p. [ 95 ] 



