MANUAL OF NATURAL HISTORY. 89 



9. Family. — Hammer-headed Sharks (Zygsenidse). 

 Head excessively elongated on either side, so 

 as to resemble a hammer; eyes remote, on the 

 lateral ends ; teeth serrated in adults. 



10. Family. — Angel-Fishes (Squatinidse). Body 



flat above and below ; mouth at fore end of 

 snout ; eyes on dorsal aspect ; pectorals large, 

 expanded anteriorly. 



11. Family. — Greenland-Sharks (Scymniidae). Head 



flat, or compressed on sides, obtusely pointed ; 

 mouth beneath ; dorsal fins without spines ; 

 gill-openings small. 



12. Family. — Fox-Sharks (Alopeciidse). Snout short 



and rounded ; teeth sharp, triangular ; bran- 

 chial openings small ; tail unequally divided, 

 upper lobe greatly prolonged, so as nearly to 

 equal length of body. 



13. Family. — Porbeagles (Lamniidse). Branchial 



openings large ; spiracles very small ; caudal 

 fin crescentic, with a lateral keel ; second dor- 

 sal and anal fin opposite each other. 



14. Family. — True-Sharks (Squalidse). Body elon- 



gate, sub-cylindrical ; head flat ; mouth con- 

 vex ; teeth sharp-edged and pointed, mostly 

 serrated ; no spiracles in adult ; dorsal-fins 

 two, the second opposite anal fin ; tail with 

 a short under lobe. 



15. Family. — Topes (Galeidge). Head flat ; snout 



pointed or blunt ; teeth in both jaws alike, 

 flat or pointed, sharp-edged, sometimes ser- 

 rated along one or both edges ; spiracles small 



