64 REPORT OF NEW JERSEY STATE MUSEUM. 
notch on outer margin below sharp point. Internasal space 
greater than nostrils are from tip of snout. First dorsal midway 
between pectoral and ventral, of moderate size. Second dorsal 
very small. Anal a little larger and inserted a little in advance. 
Caudal long, slender, and lower lobe 24% in upper lobe. A pit at 
root of caudal above and below. Pectoral short, reaching about 
opposite middle of first dorsal, and greatest width 124 in length. 
Ventral small, inserted about first third of interdorsal space. 
Color gray, paler below. Iris pale. Margin of caudal dusky in 
spirits. Length nearly 26 inches. Holly Beach. 
This small shark is only known to me from the New Jersey 
coast by the above example in the Academy of Natural Sciences 
of Philadelphia. 
Family CESTRACIONTIDE. 
The Hammer Head Sharks. 
Mouth crescent-shaped, under “hammer.” Teeth in jaws simi- 
lar, oblique, each with notch on outside near base. Nostrils 
anterior and eyes on sides of “hammer.” Last gill-opening over 
pectoral. No spiracles. First dorsal and pectorals large, and 
dorsals nearer pectorals than ventrals. Second dorsal and anal 
small. Pit at root of caudal, and notch single towards tip of fin. 
Large sharks, known at once by the singular form of the 
head, which is not quite the same in any two species. A single 
genus with 2 species on our coast. 
Genus CESTRACION Walbaum. 
The Hammer Head Sharks. 
Key to the species. 
a. Head kidney-shaped; nostril with frontal groove short or obsolete. 
TIBURO 
aa. Head hammer-shaped; nostril with well-developed groove extending 
along front of head. ZYGCENA 
