Zoology.'] NATURAL IIISTOKY OF VICTORIA. [Fishes. 



Plate 124. 



MONACANTHUS BROWNI (Rich, sr.) 

 Brown's Tooth-brush Leather-jacket. 



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

 Class Pisces. Sub-class Teleostea. Order Plectognathi. Fain. Sclerodermi.) 



Gen. Char. — Body compressed, elevated in tbe middle ; scales small, rhombic, distinct on 

 inner surface of skin, obscured by minute spines roughening 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 dorsal composed of one large thick 

 rough bony spine, which may be fixed in erect position or lowered into a pit on back, oyer 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 subtropical seas.] 



Descbiption. — Body sub-fusiform, rhombic, moderately compressed, profile 

 nearly straight, very slightly convex, rising- to a little behind the first dorsal at an 

 angle of about 25 or 30 degrees. General proportion slender, the greatest height 

 about one-third of the total length, including the caudal fin. Eye large, close to 

 the frontal level. Branchial slit oblique, nearly equalling the diameter of the eye, 

 lower end just above level of base of pectoral. First dorsal spine nearly straight, 

 irregular, slightly less than half the length from its base to the snout, placed over 

 the posterior third of the eye, quadrangular in section, the two anterior longitudinal 

 ridges with about 13 large, slightly hooked spines, directed obliquely downwards 

 forwards and outwards. Two posterior keels with much fewer and smaller spines, 

 very irregular in size, shape, and direction, most of them being directed upwards, 

 and a few outwards or downwards ; a few irregular spinous tubercles on the sides 

 between these rows. One very small ray in the membrane behind the large spine. 

 Abdominal edge narrow over the long pelvic bone, the point of which is scarcely 

 traceable, but is covered with a little plate having a few large spines at its angles, 

 and be}'ond which the ventral outline rises abruptly to the anterior base of the anal 

 fin. Fins: Pectoral semi-oval, rounded, of 13 rays. Second dorsal rising rapidly 

 to the 7th and 8th rays, with an obtusely rounded curve, continuing thence with a 

 straight edge and gradually diminishing height to the posterior end, of 33 simple 

 rays. Anal rising rapidly to the 6th or 7th ray with a rounded anterior edge, 

 thence nearly straight to the shorter rays of posterior end, composed of 32 simple 

 rays. Caudal fin rounded, of 14 thick, doubly-branched rays, set with spinulose 

 granules. Skin covered with small rhombic scales, each rising into a point having 

 a broad radiated base, in the fresh state, on some parts of the body ; the apex of 

 the spine is capped with a granular cutaneous mushroom-like expansion. On the 



[91] 



