424 Memoir Sears Foundation for Marine Research 



about as near to inner corners of pectorals as to origin of anal. Pectoral a little more than 

 % (average about 68%) as long as head, or a little longer than vertical height of ist 

 dorsal and about % as broad as long, its outer margin moderately convex, distal margin 

 nearly straight or very slightly concave, apex and inner corner very narrowly rounded. 



Color. Gray or grayish-brown above and a paler shade of the same hue below, some 

 specimens with a few small round dark spots on the sides j no conspicuous fin markings. 



Size. A female of 1,076 mm. in the Harvard Museum of Comparative Zoology 

 contains eight young of about 300 mm. nearly ready for birth. Sexual maturity is attained 

 at a length of 3 V2 to 4 feet j it is said to reach 6 feet, but few grow longer than 5 feet. 



Developmental Stages. Development is viviparous. The egg, with its developing 

 embryo, is enclosed at first in a tough but elastic shell, iridescent in appearance, the ends 

 of which are curiously plaited and folded, allowing for the growth of the embryo by their 

 expansion. After the embryo is set free from the eggshell and the yolk has been absorbed, 

 the empty yolk sac becomes attached to the uterine walls of the mother, forming a so-called 

 yolk-sac placenta richly supplied with blood vessels. The embryos are described as lying 

 with their heads toward the anterior end of the uterus. The umbilical cord may be about 

 as long as the embryo and is closely set along its whole length with large villi, some of 

 which are simple but others branched. The number of embryos (6 to 9) is much smaller 

 than in -zygaena, corresponding to their type of development, with males and females in 

 about equal numbers," 



Habits. This species occurs chiefly in shallow water, close inshore, often in bays and 

 estuaries, sometimes coming right up to wharves. It is said to be more sluggish than other 

 Hammerheads. It feeds largely on whatever crabs may be available locally and on other 

 Crustacea such as mantis shrimps (Squilla), shrimps, isopods and even barnacles. But its 

 recorded diet also includes bivalve mollusks, cephalapods (Octopus), small fish, and 

 even seaweed, the latter no doubt taken incidentally with crabs, etc. And it has been de- 

 scribed as burrowing under coral masses in search of small fish and Crustacea in southern 

 Florida waters. It takes a hook readily on almost any kind of bait and is often said to follow 

 fishing boats to pick up any fish or other scraps that may be discarded. 



Relation to Man. It is of no commercial value except for a few that may be sold in the 

 fish markets. It is entirely harmless. 



Range. Tropical to warm-temperate belt of the Atlantic from southern Brazil north- 

 ward regularly to the southern part of North Carolina and as a stray to southern New 

 England and Massachusetts Bay in the west} it apparently occurs also in tropical West 



17. For an excellent illustration of the embryo with yolk stalk and large yolk sac before the disappearance of the 

 external gills, see Lcuckart (Unters. Auss. Kiemen Rochen Hayen, Stuttgart, 1836: 22, pi. 3) ; for further ac- 

 counts of the early development of tiburo, see Gudger (Science, N. S. 55, 1912: 466; Proc. biol. Soc. Wash., 25, 

 1912: 143), Radcliffe (Bull. U.S. Bur. Fish., 40, 1916: 266) and Longley and Hildebrand (Pap. Tortugas 

 Lab., 31, 1941: 3). 



