42 
BULLETIN OE THE UNITED STATES FISH COMMISSION. 
Squalus zygxna Linnaeus, Syst. Nat., Ed. X, 234, 1758, Europe; America. 
Sphyrna zygxna, Rafinesque, Indiee d’Ittiol. Sic., 46, 1810 (Messina); Muller & Henle, Plagiostomen, 51, 1841 (Brazil; 
India) ; Jordan & Evermann, Pishes North and Mid. Amer., I, 45, 1896; Evermann & Marsh, Fishes of Porto Rico, 
63, 1900. Jenkins. Bull. U. S. Fish Comm., XXII, 1902 (Sept. 23, 1903), 120 (Honolulu); Snyder, Bull. U. S. Fish 
Comm., XXII, 1902 (Jan. 19, 1904), 515 (Molokai). 
Squalus malleus Risso, Ichth. Nice, 34, 1810. Nice. 
Zygxna malleus, Shaw, Nat. Miscell., pi. 267, 18 , — ; Gunther, Cat., VIII, 381, 1870 (Totoya, Fiji Islands); Gunther, 
Shore Fishes, Challenger, Zook, I, Part VI, 59, 1880 (Reefs at Honolulu). 
Zygxna lewini Lord in Griffith, Animal Kingdom, X, 640, pi. 50, 1834, New Holland. 
Zygxna subarcuata Storer , Proe. Bost. Soc. Nat. Hist., Ill, 1848, 70, Cape Cod. 
Ceslracion zygxna, DumOril, Elasmobr., II, 382, 1865 (Mediterranean; coasts of North and South America; Australia; Japan). 
Family V. ALOPI I DAi.— Thresher Sharks. 
Body moderately elongate, the snout rather short; mouth crescent-shaped; teeth equal in both 
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 rest of 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 tail. 
Genus 8. ALOPIAS Rafinesque. 
The characters of this genus are included with those of the family. 
Alopias Rafinesque, Caratteri di Alcuni Generi, 12, 1810 (macrounis=vulpes) . 
Alopecias Muller & Henle, Plagiostomen, 74, 1841; amended orthography. 
10. Alopias vulpes (Gmelin). Fig. 4. 
Body fusiform, cylindrical, thickest before dorsal fin; back regularly arched from above pectorals 
to end of snout, and gradually decreasing in size posteriorly to caudal. Head short, bluntly conical; 
224-22 
snout blunt; eye rather large; mouth horseshoe-shaped; teeth about third or fourth tooth on 
either side of center of upper jaw smaller than others; spiracles very small or wanting; last gill- 
openings above or slightly in front of pectorals. 
Body more or less roughened. First dorsal high, triangular, somewhat higher than its base is 
long, slightly slender toward its summit, superior angle rounded; second dorsal similar in shape, but 
much smaller; anal small, placed behind second dorsal, which it resembles; pectorals long, wide, 
emarginate, with small process behind; ventrals wider than high, nearest first dorsal; caudal nearly 
as long or longer than body, composed of 3 distinct lobes, one small, triangular, at under side of 
tip, a second long and low, extending albng upper side of tail, and a third short and broad, at lower 
base of tail. 
Color, slate-blue above, beneath soiled white, marked with obsolete bluish spots; pupil a longi- 
tudinal slit, edged with golden. 
Length, 12 feet. 
One large specimen received from the Honolulu market through Mr. Berndt. 
