CARCHABIIDjE. 7 



increases, and innumerable young swarm along the shores, while 

 they are exceedingly numerous off the low coast and muddy seas of 

 Burma. In fact I shall have to describe double the number of 

 forms given by Klunzinger : Carcliariaa 17, Hemigalew 1, Galeo- 

 cerdo 2, 



Synopsis of Genera. 

 First group. CAECHABIINA. 



Snout produced longitudinally. Teeth erect or oblique, with a single 

 cusp, which has smooth or serrated edges. A pit at the base of 

 the caudal fin. 



No spiracles .................................... 1, CABCHARIAS. 



Spiracles small. Distinct labial folds. Teeth ser- 

 rated or notched in the upper jaw. Caudal 

 fin with a single notch ...................... 2. HEMIG ALETJS. 



Spiracles small. Teeth serrated in both jaws. Caudal 



fin with a double notch ...................... 3. GALEOCEBDO. 



Second group. 



Head produced laterally into the shape of a hammer. Nostrils on front 

 edge of head. Teeth oblique, with a single cusp, having sharp 

 smooth edges. A pit at the base of the caudal fin. 



Spiracles absent ................................ 4. ZYGUENA. 



Third group. MTJSTELINA. 



Teeth small, obtuse, or having a central and one or two smaller 

 lateral cusps. 



Spiracles small; labial folds well developed. Teeth 



obtuse. No pit at base of the caudal fin ........ 5. MUSTELUS. 



No spiracles. A pit at base of the caudal fin ........ 6. TBUENODON. 



First group. CARCHAEIINA. 



1. Genus CARCHARIAS, Muller & Henle. 



Syn. Scoliodon, Aprion or Aprinodon, Physodon, Ilypoprion, Prionodon, 

 Muller & Henle ; Priotiace, Cantor ; Eulamia, Isogomphodon, Lamiopsis, 

 Platypodon, Jfypopn'onodon, Isoplagiodon, and Cynocephalus, Gill. 



No spiracles. A pit before the root of the caudal fin. Snout 

 longitudinally produced. Mouth crescentic or angular ; the labial 

 fold or groove rarely extends beyond the angle of the mouth. 

 Teeth erect or oblique, with a sharp more or less compressed cusp, 

 sometimes triangular, the edges of which may be serrated or 

 smooth*. The first dorsal fin, destitute of a spine, is placed 



* In some forms these characters alter considerably with age. 



