xrcHOLs iS; MrKi'iiv : loxc. island sharks. 3 
numerous, uiostlx" trojncal, niaii>- of them \videl\ distributed, a few 
cosmopolitan. They are without .strono- taxonomic characteristics, the 
differences between .some of them being .slight or sul^tle. I'sualh' one or 
more species of this famil\- are numerous on an\- temperate or tropical 
coast. The first dorsal fin is large and jilaced ojiposite the s])ace between 
the ])ectorals and ventrals, the .second dorsal fin is usuallx' nuich smaller. 
The head is normal in sha])e, the caudal fin not lunate and the ])eduncle 
without a median keel. 
The Sphyrnidae, or hammerhead sharks, contain a few species re- 
sembling in general the ])receding family, but with very ])eculiarl\" formed 
heads. 
The Alo]iiidce comprise but a single sy)ecies, which has an extraor- 
dinaril\- elongate tail, and is cosmo])olitan in warm seas. 
The Carchariidge, .sometimes placed with the Lamnidce, contain a 
few clo.sel>' related s]iecies belonging to a single genus, locall\- com- 
mon on usiialh' tem])erate shores of the world. Our <)ul\' s])ecies has \-er\' 
.sharp and white teeth, with a cus]) on each side at the ])ase. The 
dorsal fins are subequal in si/e, and tliere is no keel on the ])eduncle. 
The mackerel-sharks (Lanuiidcei, swift-swinuning, ])redacious, pe- 
lagic fishes, are rej^rcsented b\' a few warm-water species, which, as a 
rule, do not occur in great numbers anywhere. They ha\-e a central 
keel on the caudal peduncle, and a firm, lunate caudal fin. 
A .single sjiecies com])rises the Cetorhinidte, a huge, sluggish north- 
ern form, .straggling southward to our coast, differentiated from the 
Lamnidse, from which it ai)])ears to be derived, b\- the remarkable length 
of its gill-.slits and b\' the de\'elopment of its gill-rakers. The latter are 
probably u.sed to strain small food from the .sea-water, as is the baleen of 
whalebone whales. 
The family Squalidse, with several deep-water genera, is rej^rcsented 
on the Long Island coast b\- a northern species without anal fin and with 
a s]iine in each of its dorsals. It is conunon in winter. 
Finally the vSquatinidse, with a .single genus and onl\- two or three 
s])ecies, present a very peculiar a])i)earance, due to their flattened circular 
head, narrowed neck, and a pointed, forward prolongation of the pectoral 
fin^ 
There is something ])eculiarly sinister in the shark's make-up. The 
sight of his dark, lean fin la/.il\- cutting zigzags in the surface of .some 
