COTTID^E. 55 



Genus II. — Trigla, Arlecli. 



Hoplonotus, Guichenot. 



Branchiostegals seven : pseudobranchice present. Head parallelopiped : ivith its 

 superior and lateral surfaces bony. Villiform teeth in both jaws and usually on the 

 vomer, but none on the palatines. Two dorsal fins, the first being of less extent than 

 the second ; three free filaments at the base of the pectoral fin. Air-bladder loell 

 developed, usually provided with 'lateral muscles, and sometimes partially divided 

 internally by partitions. Pyloric appendages few or in moderate numbers. 



Trigla was the Greek term for the Mullets, Mullidcs ; Artedi united the two 

 genera, and when they were again separated this name was appropriated to the 

 gurnards. 



These fishes are commonly known as gurnards or gurnets derived from an 

 ancient British word signifying a firm or rugged structure, and as such applicable to 

 their heads. Gnildan, cnodan, or crudan, Gaelic, McAlpine. In France they have 

 the epithet Les Milans de mer. Many species are able to produce sounds when 

 beneath the water, from which has originated their Italian name organo, and 

 their French designation grondin. The Romans termed them lyres, either due 

 to their emitting sounds or else because their shapes bore a resemblance to the 

 ancient " lyre." 



The air-bladder in the British forms are exceedingly useful as a means of 

 diagnosing species, as they vary exceedingly. Their structure is interesting, as 

 they possess strong lateral muscles for the purpose of compression, thus 

 diminishing their size, and assisting the fish to sink when desired. The 

 thickness of the walls in some species, it has been suggested, may be for the 

 purpose of resisting pressure when suddenly rising to the surface from great 

 depths. M. Dufosse considers this organ as a generator of sound completely 

 independent of the other organisms in the fish. If a gurnard is placed on its 

 back and a long incision made in the abdominal walls and any viscera which 

 obstruct view are drawn to one side, it is directed that the tip of the finger 

 should be placed in contact with the air bladder and vibrations synchronous with 

 and having the same intensity as the sound produced by the fish will be felt. 

 Having isolated the organ as much as possible by delicate and rapid manipulation 

 from the rest of the body, with the exception of the vessels and nerves with 

 which it is supplied, a stethoscope provided at its mouth with a diaphragm of 

 gold-beater's skin should be applied to its anterior part ; then the nerves are to 

 be severed first on one side then on the other, when the sounds will be found to 

 decrease in intensity and finally entirely cease. He concluded that the intrinsic 

 muscles by their vibration aided and intensified by the rest of the organs are 

 the agents of the sounds produced ; while other muscles can by their contraction 

 alter the shape of the organ and thus modify the quality of the sounds emitted. 



The rough granulations along the front edge of the first two dorsal spines 

 are liable to vary in examples of the same species, in some being present and 

 well developed, whereas in others they may be entirely wanting. 



Habits. — Gurnards are rather voracious, mostly swimming near the bottom 

 of the sea where they feed on Crustacea or other small prey. 



Their free pectoral filaments, which have a certain similarity to elongated 

 fingers, are employed as feelers, used as a means of progression, or even for the 

 purpose of drawing prey towards their mouth. Their large pectoral fins, 

 although employed when balancing themselves in mid-water, are insufficient for 

 the purpose of sustaining them in the air. They live for some time after their 

 removal from the sea, and on being touched erect their dorsal spines, and at the 

 same time emit certain sounds from which many local names have had their origin. 

 These fishes, more especially T. obscura, have been reputed to emit light from the 

 head, occasioning, according to Lacepede, their passage through the air to 

 resemble the course of a shooting star. Couch observes that Risso believed this 



