34 THE PLAGIOSTOMIA. 



ISURUS. 



Isurus Rafinesque, 1810, Caratteri, p. 12. 



Lamna Cuv., 1817, Reg. anim., 2, p. 126. 



Lamna and Oxyrhina Muller & Henle, 1837, Sitzb. Akad. wiss. Berlin, p. 1141. 



Isuropsis, Isurus, and Lamna Gill, 1861, Ann. N. Y. lye, 7, p. 398. 



Snout produced, pointed. Teeth awl-shaped, with two-rooted base and 

 with or without denticles on the base. Spiracles behind the eye, sometimes 

 absent. Gill openings wide, in front of the pectoral. Pectorals large, subfalci- 

 form. First dorsal large. Caudal with a much produced lower lobe. With 

 two subgenera, Isurus and Lamna. Many Cretaceous and Tertiary species. 



Teeth with denticles at each side of the base in adults . Lamna (page 34) 

 dorsal origin above the ends of the pectorals 



second dorsal above the anal .... nasus (page 34) 



Teeth without denticles Isurus (page 36) 



dorsal origin above the pectorals 

 second dorsal above the anal 



teeth small punctatus (page 36) 



second dorsal in front of the anal 



teeth medium tigris (page 36) 



dorsal origin near a vertical from end of pectoral base 



second dorsal origin in front of that of anal . oxyrhynchus (page 37) 

 dorsal origin near a vertical from the ends of pectorals 

 second dorsal nearly in front of the anal 



teeth large, in about M rows . . . glaucus (page 38) 

 dorsal origin behind the pectoral about one length 

 second dorsal in front of the anal 



teeth in if rows "either side" . . . gilntheri (page 39) 



Isurus nasus. 



Porbeagle Borlase, 1758, Nat. hist. Cornwall, p. 265, pi. 26, f. 4; Pennant, 1769, Zool., 3, p. 92; 1776, 



Zool., 3, p. 117; Goodenough, 1797, Trans. Linn, soc, 3, p. 80, pi. 15; Yarrell, 1836, Brit, fishes, 



2, p. 384; Couch, 1867, Brit, fishes, 1, p. 41, pi. 8. 

 Squalus glaucus Gvnnek, 1770, Norsk, vid. sel.sk. skr., 4, p. 1 (nonLinn6); Ascanius, 1777, Icon., pi. 31. 

 Beaumaris Shark, Pennant, 1776, Brit, zool., 3, p. 104, pi. 17. 

 Haaebrand Ascanius, 1777, Icon., pi. 31. 

 Le Nez Broussonet, 1V80, Mem. Acad, roy., p. 667. 



Touille boeuf. Taupe de M^r, Duhamel, 1782, Traite, 4, p. 298, pi. 20, f. 4 (lacks anal fin). 

 Squalus nasus Bonnaterre, 1788, Ichth., p. 10, pi. 85, f. 350; Walbaum, 1792, Artedi, p. 517. 

 Squalus cornubicus Gmelin, 1789, Linne Syst., 1, p. 1497; Schn., 1801, Bloch Ichth., p. 132; Tubton, 



1807, Fauna, p. 113; Donovan, 1807, Br. fish., 5, pi. 108; Neill, 1811, Mem. Wern. soc, 1, p. 



549; Jenyns, 1835, Man., p. 500: Wright, Fries, & Ekstrom, 1836, Skand. fisk., p. 135, pi. 30. 



