EUASMOBRANCHII. 2j 



are 4 teeth from Monmouth County (P. D. Knieskern) ; 4 from- 

 Vincentown [The Manasquan marl, K.] in Burlington County 

 (T. M. Bryan) ; 1 from Burlington County (C. C. Abbott) ; 1 

 from Allowaystown, in Salem County (H. C. Yarrow). Orig- 

 inally there were 12 specimens in the Bryan collection, but I 

 have only examined 4. 



Order ASTEROSPONDYLI. 



THE TYPICAL SHARKS. 



Vertebral column well segmented, each segment forming a 

 neural arch and one centrum. Vertebrae each with internal cal- 

 careous lamellae radiating from central ring. Gill-openings 5. 

 Dorsal fins 2. Anal fin present. 



This order includes the greater number of living sharks. 



Sub-Order PROARTHRI. 



THE CESTRACIONT SHARKS. 



Gill-openings 5, always lateral. Palato-quadrate apparatus 

 articulated to preorbital part of skull. Dorsal fins 2, well de- 

 veloped, each with a large spine. 



Usually three families are embraced in this group, all repre- 

 sented by fossil forms, and only one, the Heterodontidce, is 

 found living, with a few species in the Indo-Paeinc. 



Family HETERODONTID^E. 

 THE BULL-HEAD SHARKS. 



Body robust in front. Head high, thick. Mouth small, nar- 

 row, 7 upper lip lobes and fold on lower lip. Teeth alike in 

 jaws, small and obtuse in front, large and m|olar behind. Nostrils 

 confluent with mouth. Gills 5. Spiracles small. Two dorsals, 

 strong spine on each. Caudal tip notched usually. Oviparous, 

 egg-cases spiral. 



Genera 15, all represented by extinct forms with Heterodontus 

 still existing. 



