Fishes of the Western North Atlantic 281 



Generic Characters. Base of anal only about as long as base of 2nd dorsal} midpoint 

 of 1st dorsal considerably nearer to origin of pelvics than to axil of pectoral; 2nd dorsal 

 only about V2 as long at base as ist dorsal and much smaller in area; spiracles lacking; 

 caudal peduncle without longitudinal ridges, but with well marked precaudal pits both 

 above and below; midline of back, between dorsal fins, smooth, without longitudinal 

 ridge; a very short labial furrow at corner of mouth and on upper jaw, but none on lower; 

 upper teeth subtriangular, oblique, with inner margins strongly convex and outer margins 

 deeply concave; lower teeth more slender, erect; uppers with finely serrate margins, 

 lowers serrate or smooth. Development viviparous, with yolk-sac placenta. Characters 

 otherwise those of the family. 



Remarks. Prionace is very closely allied to Carcharhinus but separable from it by the 

 location of the first dorsal fin relative to the pelvics and pectorals. 



Range. Cosmopolitan in tropical and warm temperate latitudes of all oceans, includ- 

 ing the Mediterranean. 



Species. The representatives of this genus generally had been considered as belonging 

 to a single wide ranging species until recently, when Phillipps" separated its New Zealand 

 representative as a new species mackei. According to Phillipps, mackei is distinguishable 

 from the Atlantic glauca by a shorter head (20% of total length as against 2S%), by a 

 shorter snout relative to its head, by pelvics larger than the anal, and by a straight instead 

 of concave distal margin of the pectoral. But these supposed differences are not consistent 

 when tested against Atlantic specimens. Among seven fish from Massachusetts Bay, for 

 example, ranging in length from about three to ten feet, the length of head from snout to 

 pectoral origin ranged from 20 to 24 per cent of the total length, it being 22 per cent in a 

 Japanese example of about 5 feet 6 inches (1,675 mm.).' The pelvics are also somewhat 

 larger in area than the anal in five Massachusetts Bay specimens of which we have meas- 

 urements, just as is the case in the New Zealand form. Neither does a comparison of the 

 outline of the pectorals of the Massachusetts Bay, Japanese and Australian specimens 

 reveal any consistent difference. The teeth, also, of an Australian specimen, as pictured 

 by Whitley,* are indistinguishable from those of the Japanese and Atlantic specimens that 

 we have examined (Fig. 47, 48). In short, we find no justification for retaining mackei as a 

 distinct species." 



6. N. Z. J. Sci. Tech., z6, 1935: 238. 



7. This is the specimen on which Garman (Mem. Harv. Mus. comp. Zool., ^6, 1913 : 145) based his description of 



glaucm. 



8. Fish. Aust., /, 1940: 95, fig. 88, 8. 



9. Phillipps (N. Z. J. Sci. Tech., t6, 1935 : 238) further states that the origin of the first dorsal in his mackei is mid- 

 way between tip of snout and rear tip of second dorsal. But his photograph of the type specimen shows it as midway 

 between tip of snout and midlength of caudal peduncle, as it is in one of the larger Massachusetts Bay specimens, 

 as well as in our Japanese example; on the other hand Whitley (Fish. Aust., i, 194.0: fig. 104) pictures it as about 

 midway between snout and origin of caudal both for Australian and for New Zealand specimens. It is evident, 

 then, that no geographic separation exists in this respect either. 



