THE LOWER FISHES 145 



Habits: This is primarily a deep-water form living at over 50 fathoms. It gets 

 closer to the surface in northern waters and at night. Probably it is a voracious 

 predator on large fishes such as dolphin, swordfish, marlin, and other sharks. 

 Except when feeding, it is probably a sluggish fish. Those who have eaten the 

 flesh report it to have a strong purgative eff"ect. 



Similar Species: The perlo or seven-gilled shark (Heftranchiis ferlo) is 

 another widespread, large, voracious fish which looks like the cow shark, but is 

 without the light, lateral line stripe and has seven gill slits. 



Galeoids: Superfamily Galeoidea 



This is the group of the great majority of modern sharks. All have five gill 

 slits and two dorsal fins which are not preceded by a spine. Because these are 

 active sharks, there is a tendency to reduce or even lose the spiracle. In 

 separating the families, the size and placement of the dorsal fins and gill slits 

 are of importance. 



CARPET SHARKS OR NURSE SHARKS: Family Ginglymostomidae 



The two large dorsal fins are both posterior to the pelvics. Gill slits three, four, 

 and five are over the pectoral fins and four and five are so close together as to 

 appear as one. The mouth is preceded by two short barbels and is connected 

 to the nostrils by a short groove. As befits bottom-living, sluggish sharks, the 

 lower tail lobe is poorly developed. These sharks are ovoviviparous. 



NURSE SHARK (gata) : Ginglymostoma cirratum— Figure 48 



Size: Averages 5 feet. Commonly up to 8 to 10 feet. Exceptionally to 14 feet. 



Distribution: Rhode Island to Brazil, but not commonly north of Cape 

 Hatteras. Also on the western coast of Mexico. 



Identification: The young have small black spots, which disappear with 

 maturation, scattered over the dingy brown body. The head is large and flat, and 

 the eyes small. 



Habits: This is a sluggish, inoff^ensive, and rather fearless shark which is very 

 common in shallow tropical waters. It is often seen lying in a protected hole or 

 cove or under a ledge near coral heads. Pairs come into very shallow water in 

 order to mate. At such times they loll about with their dorsal fins out of water. 

 It is quite a sport among local boys to grasp them by the pectoral fins in order 

 to secure a ride. When mating, the male holds the female by a pectoral fin with 

 his teeth. Thus, female nurse sharks are likely to look a bit ragged about the 

 pectorals after a few mating seasons. This shark, although normally inoffensive, 

 will definitely bite when annoyed. 



Fig. 51. Nurse shark. 



