1 68 Memoir Sears Foundation for Marine Research 



from Miami, Florida, in the same collection j fresh specimens not preserved — an adult 

 male of 13 feet taken August i, 1941 (jaws saved), a female 7 feet i inch taken June 15, 

 1943, immature males of 5 feet 2 inches (1,577 mm.) and 6 feet 10 inches (2,083 nmi.); 

 and immature female, 4 feet 10 inches (1,478 mm.) from Woods Hole, Massachu- 

 setts} also two small specimens from San Francisco and one from the west coast of South 

 America (Harv. Mus. Comp. Zool., No. 345, 519, 705). 



Distinctive Characters. The enormously elongate tail sets the Common Thresher 

 apart at a glance from all other Atlantic sharks, except for its close relative, the Big-eyed 

 Thresher. It is marked off from the latter by its much smaller eye, shorter snout, by the tip 

 of its first dorsal considerably anterior to the origin of its pelvics, by the tip of its second 

 dorsal overlapping the base of its anal, and in having about 20 teeth on each side in each 

 jaw (only about 10 in superciliosus) . 



Description. Proportional dimensions in per cent of total length. Female, 1,225 mni., 

 from Nahant, Mass. (Harv. Mus. Comp. Zool., No. 486). Male, 2,083 mm., from Buz- 

 zards Bay, Mass. (field specimen). 



Trunk at origin of pectoral: breadth 8.3, 7.3 ; height 9.6, 9.3. 

 Snout length in front of: outer nostrils 2.5, 1.75 mouth 3.6, 3.8. 



Figure 27. Alofias vulfhtus, female, about 1,300 mm. long, from Massachusetts Bay (Harv. Mus. Comp. Zool., 

 No. 1 166). A Caudal peduncle from above to show precaudal pit. B. Right-hand corner of mouth, with lips 

 separated to show single upper labial furrow. 



