90 MANUAL OF NATURAL HISTORY. 



or large ; tail-pits indistinct, or wanting ; 

 under lobe of caudal-fin abortive in some; 

 upper lobe notched. 



16. FAMILY. Spotted Dog-Fishes (Scylliidse). Snout 



generally obtuse ; teeth tricuspidate ; an anal 

 and two dorsal fins ; first -dorsal opposite, or 

 behind abdominal fins, never before ; caudal 

 none ; spiracles distinct, generally large ; 

 colours lively. 



17. FAMILY. Piked Dog-Fishes (Spinacidse). Strong, 



sharp spine before each dorsal fin ; skin 

 rough in one direction ; teeth in both jaws, 

 mostly small, sharp, and cutting. 



18. FAMILY. Gray-Sharks (Notidanidae). Head 



flat ; branchial openings six or seven, decreas- 

 ing in size from first to last ; one dorsal fin ; 

 tail-fin with a small under lobe, notched at 

 the end, obliquely or directly truncated. 



19. FAMILY. Cestracions (Cestraciontidse). Bran- 



'* chial openings small; mouth at fore-end of 

 snout; teeth pavement-like, anterior rows 

 small and pointed ; spiracles small ; a prickle 

 or sting before each dorsal fin ; tail-fin short, 

 with distinct under lobe. 



II. ORDER FALSE-SHARKS (Holocephali). 



Endo-skeleton cartilaginous ; exo-skeleton as pla- 

 coid granules ; most of the fins with a strong spine 

 for the first ray ; gills laminated, attached by their 

 margins ; a single external gill-aperture; no swim- 

 ming-bladder. 



