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 24/5 in upper lobe. A pit at 

 root of caudal above and below. Pectoral short, reaching about 

 opposite middle of first dorsal, and greatest width i J^ 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 Xew Jersey 

 coast by the above example in the Academy of Natural Sciences 

 of Philadelphia. 



Family CESTRACIONTID^. 



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 Cestraciox 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 vrell-developed groove extending 

 along front of head. zyg.5;xa 



