622 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.xxvi 



ventralsand anal; anal much longer than second dorsal, rather lower 

 pectorals short, narrow, rounded flexible rays longest; ventrals witl 

 ver}^ long base; no caudal keel; no pit at root of caudal; lower lobe o 

 caudal long and rather high, with a sharp notch near its tip. 



Color light reddish gray, brownish abov'e; fins darker l)rown; nuchal! 

 region a little darker; belly paler. (Jordan.) 



The type specinuMi, now in the Imperial University of Tokyo, wa. 

 captured in deep water off Misaki and presented l)y Capt. Alai 

 Owston, of Tokohama, for whom it is named. Captain Owston ha: 

 had engravings of this species made, and scattered them far and widii| 

 among the Japanese fishermen, but until 1902 he found no seconcj 

 specimen and no one who knew the fish. In a recent letter (Novem! 

 ber, 1!H)2) he announces the acquisition of another specimen. i 



Family X. LAMNID^. 

 MACKEREL .SHARKS. 



Sharks of large size, with the body stout, the mouth wide, wit.i| 

 large teeth, and the tail slender, the caudal fin lunate, the two lobe 

 not very unequal, the upper lobe strong!}^ bent upward; cauda 

 peduncle with a strong keel on each side; gill-openings wide, all i 

 front of the pectorals, entirely lateral, not extending under the throat 

 first dorsal large; pectorals large; ventrals moderate; second dorsr 

 and anal very small; a pit at the root of the caudal; spiracles minut 

 or absent. Numerous fossil species are know^n. In this family th 

 dentition, as well as the nuiscular system, reaches its highest degrc 

 of specialization known among sharks. 



a. Lamnin^. Teeth slender and sharp, with entire edges. 



h. Teeth without basal cusps, long, flexuous, acute; first dorsal inserted nearl 



midway between pectorals and ventrals Isuropsis, l!' 



bb. Teeth each with one or two basal cusps; first dorsal not far belund pectorals.i 



Lamnny V. 



aa. ('AKcnARODONTiN.E: Teeth with serrated edges, compressed, triangular in forn 



without basal cusp Carcharodon, 2' 



18. ISUROPSIS Gill. 

 ImropmGiiA., Ann. Lye. Nat, Hist. N. Y , VIII, 1861, p. 153 {glaums). 



Snout rather long and pointed; the body formed much like that c 

 a tunny or mackerel; first dorsal large, inserted, entirely behind pe( 

 torals, nearly midway between pectorals and ventrals; pectorals large 

 .second dorsal and anal very small; caudal peduncle slender; teet 

 long, lanceolate, with sharp, entire cutting edges and no basal cusp^! 

 ^^ {i'ffo^, equal; oiJpd^ tail; the two lobes of the tail being nearly equa 

 oi/'i?;, appearance. From /sums it is separated by the backward insei 

 tion of the dor.sal.) 



