164 



Galeods.- 



-FISHES.- 



-Sc tLLIDS. 



Order XII. — GALEODS or SHARKS. 



Squall — ( Characterized above.) 



Family I.— SCYLLIDS (ScylUUla:). 



In this family there is one dorsal fin standing over 

 or behind the veutrals, another farther back, and one 

 anal. The eye is not provided with a nictitating 

 membrane, but spout-holes exist behind the eyes. Of 

 the five stigmata the last one is over the base of the 

 broad pectorals ; at the corner of the mouth there is a 

 furrow in the integuments, and also a labial cartilage 

 above and below. The teeth have a pointed mesial 

 cusp, and from one to four denticles on each side of it. 

 I'he caudal fin is extended longitudinally, with a trun- 

 cated or r unded tip, and without an under lobe or 

 merely with the traces of one, but with a notch near 

 the end, beneath. 



Tlie family includes tlie following genera — ScyHhmi; Pris- 

 tiurus; IlemisctjUium ; ChUoscyllium ; Crossorhinus ; Cing- 

 himostoma ; and Siegostoma. 



In the British seas there have been detected the 

 Small-siiotted Dog-fish {Scyllium caniciila) ; the Largo- 

 spotted Dog-fish [SajlUam calulus) ; and the Black- 

 mouthed Dog-fish [Pristiurus mckmostomns). 



Family II.— CARCHAEIiEDANS {Carchariwdw). 



In these Sharks the first dorsal is situated over the 

 space between the pectorals and ventrals, and they 

 have also a second dorsal and an anal ; the eyes are 

 furnished with nictitating membranes, but spout-holes 

 do not exist in a pervious state in the adults; each 

 nostril is generally provided with a small three-sided flap 

 on its upper border ; the mouth has a boldly convex 

 outline, with small folds of skin at its corners ; the anal 

 fin is placed directly under or close behind the second 

 dorsal; and the caudal fin has always a short under lobe, 

 with a notch on the inferior edge of the elongated upper 

 lobe, close to its obliquely truncated end ; the intestinal 

 valve is rolled longitudinally, and is not scalariform ; 

 the scales are small, and the skin smoothish. The 

 family consists of the genera Carcharias and Prionodon, 

 and includes some of tlie Sharks that are most numerous 

 in the tropical seas, and most dangerous to mariners. 

 The Blue Shark (Carcharia sglaucus) frequents the 

 Cornish coasts, and does much injury to the fishermen 

 by cutting their lines and nets, for which its serrated 

 teeth are well adapted. 



Family III.— SPHYRN^DANS {Sphyrnwda^. 



Sharks resembling the Carcharidans in the number 

 and position of the fins, in having nictitating mem- 

 branes, and wanting spout-holes, but having the eyes 

 stilted out by a great lateral prolongation of the orbits, 



giving a form to the skull from whence comes the 

 popular name of Hammer-headed Sharks. The only 

 genus is Si'hyrna, also called Zygmna. 



The great lateral breadth of the skull, arising from 

 the projection of the orbits, gives a very strange aspect 

 to these Sharks, one of whom, Sphyrna zygcaia, or 

 the Hammer-beaded Shark, is an occasional visitant of 

 the British seas. 



Family IV.— TRIiENODONTS {Trimnodontes) . 



In this family the head is flat, and the snout is 

 sometimes pointed, sometimes blunt ; the nostril-valve 

 is broad, or less commonly lengthened out into a bar- 

 bel ; the orifice of the eye longitudinal, and the fold at 

 the corner of the mouth is very small; the teeth 

 resemble those of tiio Scyllids, but with a longer middle 

 cusp, and not more than one or two lateral denticles ; 

 the second dorsal fin and the anal are opposed to one 

 another, or neaily so, and the scales have three, five, 

 or seven keels. 



The only genus is Trianodon, an inhabitant of the 

 Indian Ocean and Red Sea. 



Family V.— GALEIDANS (Galeidcc). 



In this family there are also two dorsal fins and an 

 anal, as in the four preceding ones, but the first dorsal 

 is farther forward than the ventrals. Nictitativig 

 membranes and spout-holes are both present, and the 

 last stigma is over the base of the pectoral. Nostrils, 

 orbits, and corner folds of the mouth as in the Carcha- 

 ridans, and the small labial cartilages are always 

 present. Teeth of both jaws alike, flat, oblique, and 

 with entire or serrated cutting edges. The scales are 

 small and three-keeled, with a mesial cusp. In the 

 upper lobe of the caudal there are one or two notches. 



The genera are — G(deu$; Galeocerdo ; Loxocioti; Thalus- 

 sorhinus. 



The only British species is the Common Tope {Galmn 

 cants). Galeocerdo arcticus is not uncommon in the 

 North sea, but has not been taken among the British 

 isles, unless it should be the White Shark of the Ork- 

 neys, which has not been examined by a competent 

 ichthyologist. 



Family VI,— SCYLLIODONTS {ScylUodontkla;). 



The members of this family are characterized by a 

 flat head, blunt snout, and a moderately broad and long 

 nasal flap. The depressions at the corners of the month 

 and the labial cartilages are large, and the spout-holus 

 are of medium size. Tlie dentition and form of the fins 

 are those of the proper Scyllids, the under lobe of the 



