Commercial Shark Fishing in the Caribbean Area 23 



Well-marked labial furrow on lower and 

 upper jaw. 



Mid-line of back between dorsal fins smooth 

 without ridge. 



Night Shark, Hypoprion signatus, 

 Figure 47. 



Length of first gill opening and teeth same 



as in Sharp-Nosed Shark. 



No labial furrow on lower jaw. 



Lower teeth differ from uppers, obviously 



more slender and more erect than uppers 



and symmetrical. 



Low but unmistakable ridge along middle 



of back between two dorsal fins. 



2. Hammer or shovel-shaped head. Figures 48, 

 49, 50 and 51. 



a. Front of head not indented or scalloped in 

 mid-line. 



Bonnet Shark, Sphyrna tiburo, Figure 48. 

 Outline of head only slightly concave oppo- 

 site nostrils (if at all so). 

 Free rear tip of second dorsal not longer 

 than the front margin of the fin. 

 Rear margin of anal fin weakly concave. 



Common Hammerhead, Sphyrna zygaena, 

 Figure 49. 



Outline of head deeply scalloped opposite 



nostrils. 



Free rear tip of second dorsal considerably 



longer than the front margin of the fin and 



the rear margin of anal fin deeply concave. 



b. Front of head unmistakably indented or 

 scalloped in the mid-line. 



Hammerhead, Sphyrna diplana, Figure 50. 

 Free rear tip of second dorsal considerably 

 longer than its vertical height and at least, 

 as long as its front margin. 

 Pelvics with nearly straight front margins. 



