222 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



EXPLANATION OF PLATES. 



PLATE 1. 



Fig. 1. Campodus variabilis (N. and W.). Missourian ; Kansas and Nebraska. 

 Supposed lower dentition, X I- Tlie sympliysial series is piiotograplied 

 from an actual specimen obtained by Prof. E. H. Barbour from tbe 

 Atchison shales of Cedar Creek, Cass County, Nebraska ; the man- 

 dibular rami are photographed from a plaster cast of the specimen 

 described by St. John and Worthen in the sixth volume of the Illinois 

 Palaeontology. The original of the latter specimen was derived from 

 the Missourian of Topeka, Kansas, and is now preserved in the private 

 collection of 0. H. St. John, at Raton, New Mexico. 



Fig. 2. CestracionfrancisciGirnrd. Recent; Pacific Ocean. Lower dentition, X \- 

 The cuspidate anterior and symphysial teeth are well shown by this 

 specimen. 



PLATE 2. 



All figures are of the natural size, and photographed from the original specimens 

 without retouching. 



Fig. 3. Cladodas occidentalis Leidy. Atchison shales (IMissourian) ; Table Rock, 

 Nebraska. Outer coronal face of imperfect tooth, the lateral denticles 

 and a portion of the root being broken away. 



Fig. 4. Cladodiis hiightiaiius (Cope). Chase formation (Permo-Carboniferous) ; 

 Blue Springs, Nebraska. Inner coronal face of imperfect specimen. 



Fig. 5. Peripristis semicircidaris (Newb. and Worth.). Atchison shales (Missou- 

 rian) ; South Bend, Nebraska. Uninjured side of pathologic upper 

 tooth. 



Fig. 6. Peripristis semicircidaris (Newb. and Worth.). Atchison shales (Missou- 

 rian); Louisville, Cass County, Nebraska. Anterior aspect of upper 

 dental plate, the root partially embedded in matrix. 



Fig. 7. Peripristis semicircidaris (Newb. and Worth.). Atchison shales (Missou- 

 rian) ; South Bend, Cass County, Nebraska. Anterior aspect of upper 

 dental crown, tilted slightly upward. 



Fig. 8. Cladodas occidentalis Leidy. Neosho formation (Permo-Carboniferous) ; 

 Roca, Lancaster County, Nebraska. Apical portion of crown, showing 

 striated inner face. 



