CHECK-LIST OF CEPHALOCHOBDATES, 4'C.—0GILBY. 91 



A'^. Trunk passing gradually into tail ; ovoviviparous. 



l^. Snout much produced and saw-like, without tentacles . . . . ix. Pristeid.^. 



1-. Snout not saw-like x. Rhinobatid^. 



k^. Trunk abruptly contracted at base of tail ; oviparous . . . . xi. Rajid^. 



p. Tail slender ; dorsal fin absent or single and vestigial ; ovoviviparovis (Masticura). 



m^. Pectoral fins not produced anteriorly . . . . • . . • xii. DASYBATiDiE. 



7)1-. Pectoral fins produced anteriorly to form cephalic appendages. 



n^. Teeth usually few, some or all laterally expanded ; nostrils approximate 



xiii. Myliobatid.^. 



n^. Teeth numerous and minute, sometimes absent in one or the other jaw ; nostrils 



remote . . . . . . • . • • xiv. Mobulid/e. 



Key 2— our EUSELACHIAN SUBFAMILIES AND GENERA. 



i. CAP.CHARiiDiE : — Monotypic, v. supra. 



ii. Alopiid^ : — Monotypic, v. supra. 



iii. IsuRiD^ : — 

 a^. Isurince : — Teeth long, slender, smooth. 



61. Teeth without basal cusp 3. Isurus. 



a^. Carcharodontince : — Teeth compressed, triangular, serrated . . . . 4. Carcharodon. 



iv. ORECTOLOBIDiE : 



a^. Ginglymostotnince : — Spiracles minute. 



fti. Teeth in three series, multicuspid ; origin of second dorsal in advance of the anal 5. Nebrius. 

 o^. Orectolobince : — Spiracles large. 



c^. Lower lip with a symphysial groove ; ovoviviparous. 



rfi. Teeth dissimilar ; sides of head with a more or less interrupted series of dermal lobes 



6. Orectolobus. 

 d^. Teeth all similar, smaU and tricuspid ; sides of head without dermal lobes. 



e'. Head strongly depressed ; anal fin close to caudal .. .. ..7. Brach^lurus. 



e^. Head not depressed ; anal fin remote from caudal . . . . 8. Heteroscyllium. 



c^. Lower lip without symphysial groove ; oviparous, the egg-case bag-like. 



fK Caudal fin of moderate length 9. Chiloscyllitjm. 



p. Caudal fin greatly produced . . 10. Stegostoma. 



v. SCYMORHINIDiE : 



ai. Angle of mouth with a distinct labialfold 11. Hal.^jlurus. 



vi. Galeid^ : — 

 a^. Snout produced longitudinally, in direction of vertebral axis. 

 b^. Mustelince : — Spiracles moderate. 



c^. Teeth small and pavement-like 12. Mustei.us. 



6^. Gdlcince : — Spiracles minute ; teeth aciite, serrated, depressed. 



rfi. No pit at base of caudal 13. Galeus. 



d'. Precaudal pit present 14. Galeocerdo. 



b^. Spiracles absent ; teeth acute. 



p'^. Teeth everywhere smooth, both base and cusp. 

 p. Teeth strongly depressed. 



g^. Some of the anterior teeth enlarged, their bases swollen and rovmded 15. Physodon. 

 g'^. None of the teeth enlarged, their bases narrow .. .. .. 16. Scoliodon. 



p. Teeth erect or nearly so 17. Aprionodon, 



(.-. Bases of teeth serrated in one or both jaws, the cusps smooth. 



/ji. Teeth in lower jaw erect, in upper suberect and coarsely serrated on one or both sides of 



base Hypoprion.* 



h". Teeth in both jaws depressed, their outer bases serrated . . . . 18. Rhizoprion. 



e^. All or most teeth serrated on both base and cusp, their form variable 19. Carcharhinus. 



a^. Cestracioninoe : — Snoiit expanded laterally, at an angle to the vertebral axis 20. Cestracion. 



