414- Memoir Sears Foundation for Marine Research 



by the 2 lobes) well rounded and a little more than a right angle. Distance from origin of 

 caudal to tip of anal a little less than V3 (30%) as long as base of latter. Anal a little more 

 than twice as long as 2nd dorsal at base but only about as high vertically, its anterior margin 

 weakly convex, its posterior margin deeply concave near apex but nearly straight thence to 

 tip, its apex subacute, its free rear corner about ^/^ as long as the base. Distance from origin 

 of anal to tips of pelvics a little less than % (61%) as long as base of anal. Pelvlcs with 

 nearly straight edges, rather broadly rounded apices and narrowly rounded tips, their 

 origin about under rear tip of ist dorsal. Pectoral larger than in diplana, tudes or zygaena 

 {bigelowi more nearly resembles tiburo in this respect), its length about % (65%) that 

 of head or about equal to vertical height of ist dorsal, about % as broad as long, its outer 

 margin nearly straight basally but convex toward apex, the distal margin only very weakly 

 concave or perhaps nearly straight, its apex subacute, the Inner corner very narrowly 

 rounded. 



Color. The preserved specimens we have studied are grayish brown above and of a 

 paler tint of the same hue below, the fins without conspicuous markings. In the type speci- 

 men the anterior margin of the hammer is bordered with yellowish. No information is 

 at hand as to the color of this Hammerhead in life. 



Size. The state of sexual development of the 886-mm. specimen, on which the 

 claspers extend a little beyond the tips of the pelvlcs, suggests that this Is a rather small 

 species, perhaps becoming mature when only four to five feet long. 



Developnental Stages. Embryos have not been seen. 



Habits. Nothing Is known of its habits. 



Range. So far S. btgelowi is known only from Uruguay (type locality) and from 

 Rio de Janeiro, Brazil. Probably It is a tropical species and therefore watch should be kept 

 for it in the West Indian-Caribbean region, in the Gulf of Mexico, and around southern 

 Florida, as well as along the northern and northeastern coasts of South America. 



Remarks. This little known species seems closest to S. corona Springer, 1940, and S. 

 media Springer, 1940, of the Pacific coasts of Central and South America.'^ It is separated 

 from corona by its more broadly rounded mouth, its longer head in front of the mouth 

 relative to the distance between the nostrils (head length in front of mouth about 40 per 

 cent of distance between nostrils in bigelowiy but S5 per cent in corona), the much more 

 deeply indented anterior outline of its head in the midline, and its much more strongly 

 developed prenarial grooves. It diflFers from media, with which it shares the broadly 

 rounded mouth, in the anterior outline of its head (rounded in media), in its more erect 

 lower teeth, and in the fact that the distance between eye and nostril is relatively greater. 



Synonyms and References: 



Sfhyrna tudes (in part) Garman, Mem. Harv. Mus. comp. Zool., j(5, 1913: 159 (Carman's description was 



based in part on the spec, descr. and pictured here) ; not S. tudes Valenciennes, 1 822. 

 Sfhyrna bigelowi Springer, J. Wash. Acad. Sci., 5^, 1944: 274 (descr., ill., Uruguay). 



7a. For accounts of these, with illustrations of their heads, see Springer (Stanford Ichthyol. Bull., i [5], 1940: 

 162, 163, fig. 3, 4). 



