33 HAMMER-HEADED SHARK; DOG-FISHES. HOLOCEPHALI. 



the Cornish coast, and is extremely troublesome to the fishermen 

 during the Pilchard-fishing season, cutting their lines and nets, 

 and devouring the fish. This family contains many other forms, 

 more or less departing from the ordinary type ; amongst which 

 we may mention the curious Zygcena, or Hammer-headed Shark ; 



FIG. 37L HAMMER-HKADKI) SHARK. 



which resembles the ordinary Sharks in the form of its body, 

 but has its head prolonged into the form of a double-headed 

 hammer, with an eye in the middle of each extremity. It is 

 occasionally met with in European seas, attaining the length of 

 twelve feet ; and larger ones are said to inhabit the tropical ocean. 



589. The SCYLLIID^E, or Dog-fishes, have a pair of spiracles, 

 two dorsal fins placed behind the ventrals, and an anal fin ; their 

 branchial apertures, which are of small size, are situated partly 

 above the base of the pectoral fin. The species of this family 

 are of small size, and exceedingly abundant ; three occur off our 

 coasts. They are oviparous, depositing their eggs in the curious 

 cases already alluded to ( 578) ; and it is the empty cases of 

 the eggs of these Fish which are so commonly thrown up upon 

 our beach. 



590. The sub-order of the HOLOCEPHALI, including only the 

 single family of the CHIM.ERID.E, or Chimaras, differs from the 



