CKNTRONOTUS.] PISCES (OSSEI) ACANTHOFf. 365 



the whole head and body covered with a somewhat rough skin, the 

 roughness arising from very minute scales; opercle smooth: lateral line 

 scarcely visible: on each side of the tail a projecting horizontal keel. 

 Number of vertebrae twenty-five. (Colours.) All the under parts fine 

 silvery white : upper parts tinged with dusky blue. Young individuals 

 from twelve to eighteen inches in length, have the whole body covered 

 with little tubercles, disposed in longitudinal rows : these disappear first 

 on the back, and afterwards on the belly : they are no longer visible in 

 individuals of three feet. Cuv. 



Occasionally taken in the British seas, off various parts of the coast. 

 Common in the Mediterranean, where it is much sought after as an 

 article of food. Attacks other fish, on which it is said to prey; but, 

 according to Bloch, feeds also on vegetable substances. The stomach 

 of one examined by Fleming contained the remains of the Loligo sagit- 

 tata. But little is known on the subject of its reproduction, when the 

 intermediate part of the dorsal fin is worn away, it becomes the X. Ron- 

 deletii of Leach. 



GEN. 16. CENTRONOTUS, Lactp. 



(1. NAUCRATES, Cuv.) 

 39. C. Ductor, Nob. (Common Pilot-Fish.) 



Naucrates Ductor, Cuv. et Vol. Poiss. torn. vm. p. 229. pi. 232. 

 Gasterosteus Ductor, Linn. Syst. Nat. torn. i. p. 489. Scomber 

 Ductor, Block, Ichth. pi. 338. Pilot-Fish, Will. Hist. Pise. App. 

 tab. 8. f. 2. Yarr. Brit. Fish. vol. i. p. 149. 



LENGTH. One foot. 



DESCRIPT. (Form.) General contour a little like that of the Mackarel? 

 depth one-fifth of the whole length : length of the head contained in this 

 last four times and a half: profile slightly convex; snout transversely 

 obtuse ; lower jaw projecting a little beyond the upper : each jaw with 

 a narrow band of teeth like shorn velvet; the same on the palatines, 

 vomer, and middle of the tongue: diameter of the eye one-fifth the 

 length of the head: opercular pieces much as in the Mackarel: pectorals 

 attached a little below the middle ; oval, contained seven times and a half 

 in the whole length : ventrals very close together, a little behind the 

 insertion of the pectorals, of about the same length : first dorsal repre- 

 sented by three, rarely four, very small free spines, commencing nearly 

 in a line with the extremity of the pectorals : second dorsal commencing 

 about the middle of the body ; anterior rays longest, equalling a little 

 more than one third of the depth : anal of a similar form to this last fin, 

 and commencing beneath the middle of its length ; before it two small 

 free spines, the first hardly perceptible: caudal forked to the middle; 

 the lobes rather broad, and moderately pointed : 



B. 7 ; D. 3 or 41/26 to 28 ; A. 2/16 or 17 ; C. 17, and 8 ; P. 18 ; V. 1/5 : 

 cheeks, upper part of the opercle, and the whole body, excepting a 

 triangle above the base of the pectoral, covered with small oval scales ; 

 forehead, snout, jaws, and greater portion of the opercular pieces, without 

 scales : lateral line curved, marked by a narrow series of very small 

 elevations: sides of the tail with a projecting horizontal keel. Number 

 of vertebrae twenty-six. (Colours.) Silvery bluish gray ; deeper on the 

 back, paler on the belly : sides with five broad transverse bands of deep 

 violet. Cuv.. 



