Jordan and Evermann. — Fishes of North America. 45 



Subgenus SPHYRNA. 

 62. SI'HVKXA ZYG.EXA, (Liumuus). 



(IlAMMEK-HEADF.n SlIARK.) 



Head truly hammer-shaped; width of head about twice its length; 

 length of hinder margin of hammer nearly e(inal to its width near the 

 eye; nostril close to eye, prolonged into a groove which runs along nearly 

 the whole front margin of head; iirst dorsal large; second quite small, 

 smaller than anal; pectoral rather large. Color gray. A large voracious 

 shark, reaching a length of 15 feet or more, found in all warm seas; occa- 

 sional on our coasts from Cape Cod and from Point Concepcion south- 

 ward. (JJiiyaLva, Zygwna, the ancient name, from C^^yop, yoke.) (Eu.) 



Sqnabis ,-ygsena, LiNN/Etis, Syst. Nat., Ed. x, 1758, 234, Europe; America. 



S(ii(ahts malteits, Eisso, Ichth. Nice., 34, 1810, Nice. 



Zi/gxua malleus, SroKEH, Fish. Mass., 238,1867. 



typhyrmi zyijxna, Jordan & Gilbert, Synopsis, 25, 1883. 



Zi/gcvna leichii, Loud iu Griffith, Auimal Kiugiloiii, x, C40, 1834, New Holland. 



Zijgxna 'xharcuata, Stoker, Pioc. Best. Soc. Nat. Hist., 1848, 70, Cape Cod. 



Family XIII. ALOPIID^E. 

 (The Thresher Sharks.) 



Body moderately elongate, the anout rather short; mouth crescent- 

 shaped, teeth equal in Loth jaws, moderate sized, 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 nictitating membrane; spiracles just behind eye, minute or 

 absent; first 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 leuj^th of the tail. 

 {Lamnkhc, part, Giinther, viii, 393; genus Alopecias.) 



30, ALOPIAS, Rafinesque. 

 (Thkesher Sh.\rks.) 



Alitpias, Rafinesque, Ciiraltori di AKuiii Goneri, etc., 12, 1810, (m<tcrouriis=viilpes). 

 Alupetitis, Mi'i.i.KR A- Heni.e, I'lasiostoiiieu, 74, 1838, ameudeJ orthography. 



The characters of the genus are included above. (uAwmV, a fox, Latin, 

 vulpvs. A. ruJpes was known to the ancients as a?MT:cKlu<j, fox-like). 



63. ALOPIAS VILPES, (Gmeliu). 

 (Thresher; Fox-shark; Swingle Tail; Long-tail Shark.) 

 A large shark, abounding in all warm seas, especially in the Mediter- 

 ranean .and Atlantic. It is also frequently taken on our Pacific coast. 

 (vulpes, fox.) (Eu.) 



