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



Plate 56, Fig. 1. 



ZYG^NA MALLEUS (Shaw). 

 The Hammer-headed Shark. 



[Genus ZYG-^NA (Cuv.). (Sub-kingd. Vertebrata. Class Pisces. Order Plagiostomata. 

 Sub-ord. Selachoidea. Fam. Carchariidse.) 



Gen. Char. — Body fusiform, gradually tapering to end of tail ; an anal and two dorsal fins ; 

 1st dorsal fin without spines, opposite the space between the pectoral and ventral fins ; caudal 

 fin with a notch and a pit at its commencement ; head broad, flattened, and elongate laterally 

 with two oblong lobes, at the outer edge of which the eyes are placed, with a nictitating membrane. 

 Nostrils on front edge of head ; no spiracles ; mouth semicircular, inferior ; teeth of both jaws 

 similar, oblique, with notch on outer side between pointed central cusp and base, smooth when 

 young, serrated when old]. 



Description. — Ends of the transverse hammer-head nearly as wide as their 

 posterior margins ; nostrils near the eyes on anterior edge of head, prolonged in 

 groove along greater part of front margin. Color : ashy brownish-grey above, 

 whitish below ; iris yellowish-white. 



Reference. — Squalus zygceyia (Lin.), Syst. Nat., p. 399 ; Zygcena malleus 

 (Shaw), Nat. Misc., t. 267. 



Our Australian specimens of this most singularly shaped Shark 

 are perfectly identical with those of the Mediterranean and English 

 coast. The old Greek writers who describe the Fish named it 

 Zygcena from the resemblance of the head to their balance, and 

 they give the most exaggerated accounts of its ferocity. Oppian 

 and ^lian refer to it as a source of danger to mariners, although 

 curiously enough Pliny omits to mention it at all. The small size of 

 the mouth and teeth prevents it really doing any very serious harm 

 to large anunals, and although active and fierce in habits "the 

 monstrous balance-fish of ugly shape " is not very formidable. 



The follomng are the dimensions of an averge sized sj)ecimen : — 



Measurements. 

 Total length 

 Length from front to origin of dorsal 



„ of base of dorsal 

 Height of dorsal ... 

 Length from front to anterior base of 2nd dorsal 



„ of base of 2nd dorsal 

 Height of anterior part of 2nd dorsal 



„ of posterior lobe 

 Length from anterior origin of base of caudal fin to tip 

 Depth of lower lobe of caudal 



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