OXYNOTUS. 189 



Dorsal spines with lateral grooves; a notch below the terminal fin 

 teeth one cusped, unlike in the two jaws; nostrils oblique 

 inner angle of the pectorals produced 



scales subsessile, with converging keels and stout peduncle 



Cenlrophorus (page 196) 

 inner angle of pectorals not produced; nostrils oblique 



scale crowns pinacoid, rounded, excavated or smooth, on slender 



peduncles Centroscymnus (page 203) 



scale crowns clypeoid, keeled or grooved 



upper teeth in three groups . . Centroselachus (page 200) 

 scales pedunculate, with three strong, produced keels 



Scymnodon (page 207) 

 inner angles of pectorals not or hardly produced; nostrils transverse 

 scales leaf-shaped, stalked, with a strong median keel 



Lcpidorhinus (page 211) 

 scales tricuspid, tridigitate, slender in stalk and cusp 



snout much produced . . Acanthidium (page 215) 

 teeth pluricuspid; nostrils slightly oblique 

 scales unicuspid, slender, pointed 



teeth pluricuspid in the upper jaws only 



Etmopterus (page 221) 

 teeth pluricuspid in both jaws . Centroscyllium (page 230) 



Oxynotus. 



Oxynotus Rafinesqde, 1S10, Indice, p. 45, 60. 

 Centrina Cuv., 1817, Reg. anim., 2, p. 130. 



Body stout and subtriangular in the middle, slender and compressed in the 

 tail. Head small, depressed, flattened somewhat on the crown. Snout broad, 

 obtuse. Nostrils anterior, valves broad. Mouth transverse, with labial folds 

 and grooves, and a lip. Teeth unlike in the two jaws; upper slender, in a narrow 

 group; lower compressed, triangular, serrated, functional in single series, except, 

 perhaps, when about to be shed. No nictitating folds. Spiracle rather large. 

 Two dorsals, with deeply imbedded spines, the anterior spine rising obliquely 

 forward. No anal fin. Scales uniform, rough. Fossil in Pliocene. 

 Interdorsal space long, nearly twice the length of second dorsal 



scales three cusped centrum (page 190) 



Interdorsal space short, equal length of second dorsal 



scales five cusped . bruniensis (page 191) 



