262 ' HISTORY OF THE FISHES OF MASSACHUSETTS. 



GENUS VII. ZYG^NA. Cuv. 



Head depressed, more or less truncated in front ; the sides extend horizontally to a 

 considerable length, with the eyes at the external lateral extremity. Teeth of the same 

 shape in the upper and lower jaw, namely, the points directed toward the corner of the 

 mouth, with a smooth edge when young, but distinctly serrated in adult specimens. 

 Branchial openings, five. Two dorsal fins, — the first in a line close behind the pecto- 

 rals ; the second, over the anal fin. 



Zyg^ena Malleus, Val. 



TJie Hammer-headed Shark. 



(Plate XXXVIII. Fig. 3.) a. Head beneath.) 



Squahts Zygcena, Hammer-headed Shark. Mitch. Trans. Lit. and Phil. Soc. of N. Y., i. p. 284. 

 Zygoma Malleus, Val. Mem. du Mus. D'Hist. Nat. v. 9. p. 283., pi. 2, fig. a, 1, 6. 



«' " The Hammer-headed Shark, Storek, Bost. Journ. Nat. Hist. iv. p. 185. 



" •' Val., Synopsis, p. 256. 



" Dekat, Keport, p. 362. pi. 62, fig. 204. 



Color. The upper part of body a dark 'grayish brown, lighter on sides ; beneath, 

 white ; posterior inferior parts of head, bluish ; anterior margin of head tinged with white. 



Description. Head somewhat rounded anteriorly, semicircular directly in front, with 

 a smaller curve on each side of this, widely expanded and much compressed at sides. 

 The external margin of the sides of the head rounded, having the eyes situated at their 

 anterior extremity ; the anterior angle in front of the eyes is very prominent. The 

 width of the head is equal to twice its length, and is also about the length of the upper, 

 lobe of the caudal fin, and one fourth the length of the fish. The expanded sides of the 

 head are two thirds the length of the head. The nostrils are situated beneath and front 

 of this angle, hi the extremity of an emargination that extends along the smaller curves 

 previously mentioned. The posterior portion of the head is bordered by a stout, fleshy, 

 and concave membrane. The eyes are large and prominent. The mouth is situated be- 

 neath ; its posterior angles on a line with the posterior edges of the head. Several 

 rows of sharp teeth are seen in each jaw, — their points are directed toward the sides, 

 and have a prolonged base. Branchial apertures, five. The under surface of the head 

 aboimds in mucous pores, disposed in patches, the largest of which is of a triangular form, 

 and directly in front. 



