PSA.] 



PISCES. 



609 



inferior surface is plane, in a general 

 way conforming to that of the crown, 

 and even possessing distinctive charac- 

 teristics as applied to species ; it shows 

 in the perfect state a rather dense, 

 thin layer, perhaps in degree rather 

 than structurally differing from the more 

 cellulose middle layer composing the 

 bulk of the base, and usually marked by 

 more or less distinct longitudinal 

 grooves, or smooth and faintly keeled 

 nearest the inner articular border. 

 Type P. porosus. 



angularis, Newberry & Worthen, 1866, 

 Geo. Sur. 111., vol. 2, p. 107, Kaskas- 

 kia Gr. 



antiquus, Newberry, 1857, Bull. Nat. 

 Inst., Up. Held. Gr. 



bretonensis, Whiteaves, 1881, Can. Nat., 

 vol. 10, Carboniferous. 



FIG. 1164 Psammodus porosus. 



cselatus, St. John & Worthen, 1883, Geo. 

 Sur. 111., vol. 7, p. 217, St. Louis Gr. 



crassidens, St. John & Worthen, 1883, 

 Geo. Sur. 111., vol. 7, p. 218, St. 

 Louis Gr. 



glyptus, St. John & Worthen, 1883, Geo. 

 Sur. 111., vol. 7, p, 209, Up. Burling- 

 ton Gr. 



FIQ. 1165. Diagram of Psammodus springeri. 

 a, Mandibular series; 6, transverse profile; c, 

 longitudinal profile. 



grandis, St. John & Worthen, 1883, Geo. 



Sur. 111., vol. 7, p. 211, Keokuk Gr. 

 lovianus, St. John &*Worthen, 1883, Geo. 



Sur. 111., vol. 7, p. 207, Burlington Gr. 



plenus, St. John & Worthen, 1883, Geo. 

 Sur. 111., vol. 7, p. 213, St. Louis Gr. 



FIG 



1166. Diagram of Psammodus springeri. 

 a. Maxillary series; b, transverse profile; c, 

 longitudinal profile. 



porosus, Agassiz, 1843, Recherch. Poiss. 

 Foss., t. 3, p. 112, Kaskaskia Gr. 



FIG. 1167. Hypothetical diagram, showing me- 

 dian dental plates of Psammodus springeri. 



reticulatus, Newberry & Worthen, 1866, 

 Geo. Sur. 111., vol. 2, p. 109, Kaskas- 

 kia Gr. 



IG. 1168. Hypothetical diagram of Psammodus 

 turgidus. 



rhomboideus, Newberry & AVorthen, 1866, 

 Geo. Sur. 111., vol. 2, p. 110. syn. for 

 Sandalodus Isevissimus. 



