36 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 119 



perpendicular to the body axis; anterior margin of lower caudal lobe 

 weakly convex; posterior margin of lower caudal lobe nearly straight. 



Anterior margin of rostral node of chondrocranium nearly straight, 

 or with a broad, very shallow median indentation; accessory rostral 

 cartilages absent; anterior fontanelle (viewed ventrally) rather deep 

 and evenly rounded, with no noticeable median notch; short, rounded 

 wings present on sides of rostral node; anterior wing of olfactory 

 cartilage absent, represented only by a small "bump"; anterior part 

 of preorbital process long and slender, and without a sharp angle 

 on anterior edge; posterior part of preorbital process terminating in an 

 evenly rounded knob. 



Total number of vertebrae 196 (in one specimen examined); body 



vertebrae 101, there being six more body than caudal vertebrae. 



^ ,, 13 to 15-0 or 1-13 to 15. , ,, , , . • i 



Teeth — , , , ,^ — — , teeth weakly serrate m large m- 



12 to 14-1-12 to 14 -^ ^ 



dividuals; first upper tooth nearly symmetrical and erect; subsequent 

 upper teeth strongly oblique, their inner margins straight or evenly 

 convex, their outer margins deeply incised and with the outermost 

 teeth with very small, though well-developed cusps; lower teeth 

 similar to upper, though smaller; first four teeth in lower jaw rather 

 erect and with narrow cusps; one small symmetrical tooth at sym- 

 physis of lower jaw, none or one in upper jaw; one to two series of 

 teeth functional along sides of upper jaw, and two to three series 

 functional toward center; two to three series functional in lower jaw. 



Dermal denticles (examined from upper part of back beneath first 

 dorsal fin) closely overlapping, the blades thin and moderately arched; 

 length of denticle (measured to tip of median marginal "tooth") as 

 great, or nearly as great, as width; small specimens usually with 

 thi-ee, large specimens with up to seven, sharp-toothed ridges, and 

 from three to five pointed marginal teeth present on denticle; median 

 tooth on denticle slightly longer than more distal teeth; pedicel very 

 short. 



Individuals deep olive to brownish gray dorsally, shading to white 

 ventrally; tip of ventral sm'face of pectoral fin sometimes faintly gray 

 black in life. 



Maximum total length probably between 12 and 13 feet. 



Range. — Sphyrna zygaena has an antitropical distribution, occur- 

 ring in cooler waters of both the Northern and Southern Hemispheres 

 but apparently absent from the intervening warmer areas (map 2). 

 It is present in the western Atlantic from Nova Scotia and northern 

 New England south to (occasionally) southern Florida (UMML 5639 

 and UMML 10444), and from Argentina and Uruguay to (probably) 

 northern Brazil (exact northern limits of range in South American 

 waters uncertain). Stewart Springer (pers. comm.) states that he 



