222 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 
EXPLANATION OF PLATES. 
PLATE 2. 
Fig. 1. Campodus variabilis (N. and W.). Missourian; Kansas and Nebraska. 
Supposed lower dentition, X 4. The symphysial series is photographed 
from an actual specimen obtained by Prof. E. H. Barbour from the 
? 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 O. H. St. John, at Raton, New Mexico. 
Fig. 2. Cestracion francisci Girard. 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. Cladodus occidentalis Leidy. Atchison shales (Missourian) ; Table Rock, 
Nebraska. Outer coronal face of imperfect tooth, the lateral denticles 
and a portion of the root being broken away. 
Fig. 4. Cladodus knightianus (Cope). Chase formation (Permo-Carboniferous) ; 
Blue Springs, Nebraska. Inner coronal face of imperfect specimen. 
Fig. 5. Peripristis semicircularis (Newb. and Worth.). Atchison shales (Missou- 
rian); South Bend, Nebraska. Uninjured side of pathologic upper 
tooth. 
Fig. 6. Peripristis semicircularis (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 semicircularis (Newb. and Worth.). Atchison shales (Missou- 
rian) ; South Bend, Cass County, Nebraska. Anterior aspect of upper 
dental crown, tilted slightly upward. 
Fig. 8. Cladodus occidentalis Leidy. Neosho formation (Permo-Carboniferous) ; 
Roca, Lancaster County, Nebraska. Apical portion of crown, showing 
striated inner face. 
