i68 CRETACEOUS AND TERTIARY FISH. 



Tooth with crown compressed, elongate, acuminate, with entire 

 keel extending along each edge to base, and transverse section 

 elliptical. Enamel of crown smooth. Root about equal in length 

 to crown, conic continuation of crown apparently, and below hol- 

 low. Length 28 mm. 



Formation and locality. Originally from the Cretaceous 



Fig. 103. — Ischyrhiza mira Leidy. Haddonfield (Ford). 



greensand and No. 5. I have examined a single tooth, described 

 above, in the matrix or Hadrosaurus clay from Haddonfield (J. 

 Ford). [The specimen from Haddonfield is referable to the 

 Woodbury clay; from Harrisonville (Cope) to the Hornerstown 

 marl or Vincentown limesand, K.] 



Order ACANTHOPTERI. 



THE SPINY RAYED FISHES. 



Mouth edge formed by premaxillary. Maxillary normally 

 distinct, always present, sometimes ossified with premaxillary. 

 Shoulder-girdle connected by post-temporal with skull. Post- 

 temporal normally furcate, usually not ossified with skull. Hy- 

 percoracoid and hypocoracoid distinct, ossified, former usually 

 perforate. No mesocoracoid or interclavicles so far as known. 

 Pharyngeals well developed, lower rarely united, third upper 

 largest, fourth often absent. Opercular apparatus complete. 

 Front vertebras unmodified, without ossicula auditus. Gill-open- 

 ing before pectorals. Gills laminated. Air-vessel typically with- 

 out duct in adult. Scales variable, typically ctenoid. Lateral 

 line usually extends high. Front dorsal and anal rays typically 



