26 CONTRIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY IV. 
beueath ; liead 4.\ in leiigtli, (i to tip of caudal ; width of head slightly 
less than length of liead. L. 3 to 0 feet or more. Atlantic Ocean; 
abundant southward; ranging to China. 
{Siiualns iihtiru L. Syst. Natura! : Zijijivua iibiiro Giiuther, viii, ;{82.) 
as.— SP1IYK]\A Rafinosquc, 1810. 
Ham m er-Ji cad S h arks. 
( Ceatracion (Klein) Gill; Zygcena Cuvier; preoccupied.) 
(Raliues([ue, Carattcri di Alcuiii Nuovi Geueri, etc. : type Squahis zijgwna L.) 
Head truly “hammer ’’-shaped, the anterior, lateral, and posterior mar- 
gins distinct; nostrils near the eyes, the openings confluent with a 
groove, whicli extends along most of the front margin of the head. 
Species few, reaching a large size; found in all warm seas, a 
hammer.) 
32. §. (L.) M. & H. — Hammer-headed Shark. 
Width of head about twice its length; flrst dorsal large; second quite 
small, smaller than anal ; pectorals rather large ; color gray. A hpjge 
shark, found in all warm seas; common on our coast Itoiu Cape Cod 
southward. 
{Squalus zyijaaia L. Syst. Natui'ic : Zygwna mallenn Giiuther, viii, 381 : Zygcena maJ- 
leiif! Storer, Fish Mass. 238.) 
Super-family LAMNOIDEA. 
{The Lamnoid Sharks.) 
Family IX.— ALOPIID^E. 
{The Thresher Sharks.) 
Body moderately elongate ; the snout rather short ; mouth crescent- 
shaped ; teeth equal in both jaws, moderate siz(‘d, flat, triangular, not 
serrated; the third tooth of the upper Jaw on each side much smaller 
than the others ; gill-openings moderate, the last one above the root 
of the pectorals; no nietitafin/i membrane; spiracles just behind eye, 
minute or absent; flrst dorsal large, midway between pectorals and 
ventrals; second dorsal and anal very small; caudal fin exceedingly 
long, about as long as the rest of the body, a pit at its root, a notch on 
the upper lobe near its tip ; lower lobe moderately developed ; no caudal 
keel; ventrals rather large; pectorals very large, falcate. A single 
species, reaching a large size, inhabiting most seas ; known at once by 
the great length of the caudal tin. {Lanmidce, part, Giinther, viii, p. 393 ; 
genus Alopecias.) 
