1G2 THE PLAGIOSTOMIA. 



Galeorhinidae. 



Body elongate; head and snout depressed; tail compressed. Eyes lateral, 

 with a nictitating fold in the lower lid. Nostrils below the snout. Mouth 

 inferior, crescentic. Teeth small, in numerous rows, several series in function, 

 cuspidate to flat, in bands or in pavement. Spiracles present or absent. Two 

 dorsal fins, without a spine, first above the space between pectorals and ventrals. 

 An anal. 



Teeth compressed, cusps three to five, a number of series in function 

 spiracles absent; a nictitating fold 

 teeth with shorter lateral cusps 



subcaudal lobe produced; a caudal pit . Triaenodon (page 162) 

 subcaudal lobe rudimentary; no caudal pit Leptocharias (page 164) 

 spiracles present; a nictitating fold; no caudal pit 



teeth three cusped; labial folds long . . . Triakis (page 165) 

 Teeth in pavement ; labial folds long; subcaudal lobe not produced 

 spiracles present; a nictitating fold; no caudal pits 



teeth blunt or with rudimentary cusps . . Galeorhinus (page 169) 

 teeth with flattened crowns; nasoral grooves Scylliogaleus (page 179) 



Triaenodon. 



Triaenodon Muller & Henle, 1S37, Sitzb. Akad. wiss. Berlin, p. 113; 1S37, Wiegru. arch., p. 396; 

 1841, Plagios., p. 55. 



Trunk shaped like that of Galeus; head depressed; snout short, broad. 

 Crown broad, convex. Mouth greatly arched; labial folds rudimentary. Eyes 

 lateral, with a nictitating membrane. No spiracles. Teeth equal, small, numer- 

 ous, with a stronger median cusp and one or two small lateral cusps at each side 

 of it. Hindmost gill clefts above the pectorals. First dorsal above the space 

 behind the pectorals; second dorsal above the anal. Caudal with a pit at its 

 root above; subcaudal lobe well developed. Scales small, 3-7 keeled. 



Dorsal origin at a distance from the pectorals 



second dorsal little larger and little forward of anal . obcsus (page 163) 

 Dorsal origin close behind bases of pectorals 



second dorsal and anal subequal .... obtusus (page 163) 



