Zoology.'] 



NATURAL HISTORY OF VICTORIA. 



\_Fishes, 



Plate 88. 



ALOPECIAS VULPES (Linn. sp.). 



The Thresher, or Long-tailed Shark. 



[Genus ALOPECIAS (Mull, and Hen.), (Sub-kiugd. Vertebrata. Class Pisces. Order 

 Plagiostomata. Sub-order Selachoidea. Family Lamniidse.) 



Gen. Char. — First dorsal fin opposite to the space between the pectoral and ventral fins ; 

 the second dorsal and anal fins very small ; the anal a little behind the second dorsal. Caudal 

 fin of extraordinary length, with a pit at its base. No nictitating eyelid. Spiracles very 

 minute, close behind the eye. Teeth nearly alike in both jaws, no middle tooth, the upper a 

 little oblique, of moderate size, the third on each side in upper jaw much smaller than the 

 adjoining ones, flat, triangular, with smooth edges. Gill-openings small or of moderate width, 

 the two last very close together and over the base of the pectoral. Skin nearly smooth, with 

 very minute scales, each with three slight keels.] 



Description. — Body cylindrical until near tail, when it is strong-ly compressed 

 laterally. Snout obtusely pointed, its leng-tli sliohtly less than the distance apart of 

 the orbits. Mouth small. Nostrils very small. Pectorals very long-, narrow, falcate, 

 with a distinct posterior lobe at base. First dorsal high, triangular, with a projecting* 

 posterior lobe at base. Ventrals moderate, with a very long, narrow posterior lobe 

 at base. Second dorsal very small, a little in. front of the anal, which is similar in 

 size and shape, each being- oblong- with a very long-, slender prolongation of the 

 posterior terminal angle. Pit above at base of caudal, with a prominent ridg-e in 

 front of it. Upper lobe of caudal excessively long-, much compressed, gradually 

 tapering- to a narrow, rounded distal extremity, bordered below by a narrow fin, 

 widened into a small lobe near the point. Lower lobe of caudal triangular, of 

 moderate size. Gill-openings very small, the two hinder gill-openings behind the 

 anterior edge of the pectorals. Color: Above, dull bluish-grey, fading- to whitish 

 on the belly, with intermediate, irregular, grey, cloudy spots. 



^Measurements. 



Length from tip of snout to base of upper lobe of caudal 



„ of upper lobe of caudal ... 



„ of lower lobe of caudal ... 



„ from tij) of snout to anterior edge of orbit 

 Diameter of orbit 



Length from posterior edge of orbit to spiracle ... 

 Diameter of spiracle ... 

 Length from tip of snout to nostril 



„ of nostril 



„ from tip of snout to anterior edge of mouth 



„ „ „ „ gill-opening 



„ „ „ base of pectoral 



„ „ „ „ 1st dorsal 



„ „ „ „ 2nd dorsal 



„ „ posterior edge of last gill-opening 



„ „ anterior base of ventral 



„ „ „ edge of anal fin 



Height of 1st gill-opening 

 „ last gill-opening 



[ 27 ] 



