164 Galeods. FISHES. Scyllids. 
Order XII. — GALEODS or SHARKS. 
Squali. — [Characterized above.) 
Family I.— SCYLLIDS (Scylliidm). 
In this family there is one dorsal fin standing over 
or behind the ventrals, 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. 
The caudal fin is extended longitudinally, with a trun- 
cated or rounded tip, and without an under lobe or 
merely with the traces of one, but with a notch near 
the end, beneath. 
The family includes the following genera — Scyllium ; Pris- 
llurus ; Hemiscyllium ; Chiloscyllium ; Crossorhinus ; Ging- 
lymostoma ; and Stegostoma. 
In the British seas there have been detected the 
Small-spotted Dog-fish {Scyllium canicula) ; the Large- 
spotted Dog-fish {Scyllium cahdus) ; and the Black- 
mouthed Dog-fish {Pristiurus melanosiomus). 
Family II. — CARCHARIiEDANS {Carcharicedce). 
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 
fui nished 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 Carc/iarias and Prionodon, 
and includes some of the 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. — SPHYRNiEDANS {Sphyrncedoi). 
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 Sphyrna, also called Zygcena. 
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 zygccna, or 
the Hammer-headed Shark, is an occasional visitant of 
the British seas. 
Family IV. — TRI.®NODONTS {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 the 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 nearly so, and the scales have three, five, 
or seven keels. 
The only genus is Tricenodon, an inhabitant of the 
Indian Ocean and Red Sea. 
Family V.— GALEIDANS {Galeidm). 
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. Nictitating 
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 — Galeus; Galeocerdo; Loxodon; Thdlas- 
sorhinus. 
The only British species is the Common Tope {Galeus 
canis). 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 {Sctjlliodontidce). 
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 mouth 
and the labial cartilages are large, and the spout-holes 
are of medium size. The dentition and form of the fins 
are those of the proper Scyllids, the under lobe of the 
