128 Memoir Sears Foundation for Marine Research 



of about the same size. Pelvics originate posterior to rear tip of ist dorsal by a distance 

 about equal to distance from tip of snout to mouth, or slightly greater, their corners 

 rounded, their outer margins concave. Claspers of male long and slender, reaching about 

 % of the distance to origin of anal. Pectoral about as long as distance from posterior margin 

 of eye to 5th gill opening, or about twice as long as vertical height of i st dorsal, a little less 

 than V2> or about 45%, as broad as long, the outer margin slightly convex, the tip and 

 inner corner rounded, the rear margin moderately concave. 



Color. Described as deep blue-gray above when fresh caught,"" but appearing cobalt 

 or ultramarine blue in the water j snow-white below; dark slate gray above after preser- 

 vation, and bluish white to pale dirty gray below, on head and body, and on lower surface 

 of pectoral, with gradual transition from one shade to the other along the middle of the 

 trunk. 



Size. While the Mako is said to reach a length of 13 feet (4m.), the maximum length 

 reported for an actual specimen of this species is only about 1 2 feet.'" 



The largest West Atlantic specimen of which we find definite record, taken ofiF St. 

 Petersburg, Florida, was about 10 feet 6 inches long; one nearly as large (10 feet, 2 

 inches) was taken off New York Harbor many years ago. Males are sexually mature, as 

 indicated by the claspers, at perhaps six feet, females perhaps not until somewhat larger. 

 Recorded weights at different lengths are about 135 pounds at 6 feet; 230 pounds at 7 feet 

 8 inches; about 300 pounds at 8 feet; 1,009 pounds at lO feet 6 inches. A weight of 700- 

 800 pounds may be expected at about 9 feet, depending on condition. The largest speci- 

 men so far caught on rod and reel was one of 786 pounds taken off Bimini, Bahamas, by 

 Ernest Hemingway in 1936. The largest Pacific Mako (glaucus) yet taken on rod and 

 reel, by E. White-Wickham off New Zealand, weighed 798 pounds. 



Developmental Stages. Embryos, like those of other members of the family (p. 116), 

 are provided with a voluminous yolk stomach, and before birth they reach a very large size 

 relative to that of the mother. Presumably the number of young in a brood is correspond- 

 ingly small, but no definite information is at hand."* 



Habits. This is one of the most active and strongest swimming of sharks, famous for 

 its habit of leaping clear of the water under natural conditions and when hooked. It ap- 

 pears to be typically a near-surface fish, often seen swimming on sunny days with the tips 

 of first dorsal and caudal fins above the water. Around the Canary Islands it is often 

 hooked at depths of from five to eight meters, but we have no definite information as to 

 how deep it may descend. Nothing is definitely known of its breeding habits, but presum- 

 ably it is similar in these to its more familiar relative, nasus (p. 117). 



Very little is known of its diet other than that it is a fish-eater, preying upon the 



32. Shown as dark slaty blue above and grayish white below in colored sketch of a fresh 8-foot 4-inch specimen, 

 by J. Henry Blake, Provincetown, Mass., October 1868. 



33. 3.7 mm. calculated from the size of the jaws (Uriarte and Mateu, Notas Inst. esp. Oceanogr., 55, 1931 : 12) j 

 specimen from the Canaries. 



34. Vaillant (Bull. Soc. philom. Paris, [8] x, 1889: 38) reports an embryo of this species from the Mediterranean, 

 50 cm. long, including caudal, with yolk stomach 23 to 24 cm. long; size of the mother is not known. 



