Zoology.-] NATURAL HISTORY OF VICTORIA. [Fishes. 



on its anterior half,. enclosing an oblong- dark grey patch; posterior part of back, 

 belly, and base of tail dark grey; 3 bright ultramarine-blue stripes surround 

 the mouth, with a dull yellow one behind each; 3 or 4 long, fiexuous, narrow 

 stripes of bright blue extend from the throat along the belly, the two lowest 

 joining from one side to the other, one in front and one behind the vent, the next 

 lower one at the base of the anal fin ; the upper one continued in a loop at the 

 base of the caudal, and extending thence a little below the dorsal margin, nearly 

 to the base of the anterior dorsal spine, with a dull yellow streak below it on the 

 middle of the back, and two rows of numerous blue spots above it, and 2 or 3 

 rows of dark-purplish spots below, between it and the middle yellow patch ; 2 or 3 

 short blue streaks radiate from the eye in front. All the fins with nearly colorless 

 membrane and sap-green rays, with a bluer tinge on the caudal ; caudal fin with a 

 broad semilunar black band from the upper to the lower angle; a narrower band 

 along the upper and the lower edge, and a narrower band of black at the base. Iris 

 bronze-yellow. Measurements : Total length from snout to end of caudal, 1 ft. 1 in. 

 6 lines. Proportional measurements to total length as unity : Snout to anterior end 

 of orbit, y 1 ^ ; greatest depth of body, ^\ ; greatest thickness behind head, y 1 ^ ; 

 diameter of eye, T %^; height of 1st dorsal spine, y^; distance of base from edge 

 of upper teeth, -yYo 5 length of branchial slit, T ^; length of pectoral, T ^; 

 length of 2nd dorsal, -y 2 ^ ; greatest height of ditto, t £q ; from snout to anterior 

 ray of ditto, ■£?■§ ; from snout to anterior ray of anal, T ^ 4 o '■> length of anal, T 2 S 3 ^ ; 

 greatest height of anal, i^; length of caudal, -jW Number of. scales in space of 

 3 lines about middle of body, 8. 



Reference. — = Balistes hippocrepis, Quoy and Gaim., Voy. Uran. Zool., p. 

 212; = Aluterius variabilis, Rich. Voy. E. and T. Fish, p. 67, t. 53, f. 1 to 7. 



The "Leather-jackets," as the species of Monacanthus are 

 popularly called, are numerous in Australia, and are remarkable 

 for the varied character of the small roughnesses which cover the 

 skin outside, obscuring the scales, which are, however, distinctly 

 visible^on the inner side ; these roughnesses are sometimes pointed 

 spines, or with variously bent or dilated tips. The spine of which 

 the first dorsal fin is mainly composed, when raised is fixed in that 

 position immovably by a short, thick, bony piece falling under a notch 

 in its base ; the spine cannot be lowered until this so-called trigger- 

 bone is depressed. They all have a long pelvic bone forming the 

 abdominal outline, and terminating in a more or less distinct point 

 or spine in front of the anus, sometimes absent, and sometimes with 

 a radiated or variously sculptured base. Those having the pelvic 

 spine constitute the genus Monacanthus of Cuvier, and those with- 

 out it his Aluterius ; but nearly all subsequent writers agree in 

 uniting- those groups under the first name. The sides of the tail 

 have generally 4 or 6 conspicuous arched spines directed back- 

 wards or forwards. These are smaller or absent in the females. 



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