98 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
EXPLANATION OF PLATES. 
PLATE 1. 
Campodus variabilis (Newb. and W.) Coal Measures; Cedar Creek, Nebraska. 
Symphysial dentition, belonging presumably to the lower jaw, and displaying 
eleven fused teeth, viewed from the right-hand side. Reproduced from a photo- 
graph by Mr. A. Hyatt Verrill without retouching. Original preserved in the 
Museum of the State University of Nebraska. X 4. 
PLATE 2. 
Campodus variabilis (Newb. and W.). Coal Measures; Osage County, Kansas. 
Symphysial dentition belonging presumably to the lower jaw, with naturally 
associated antero-lateral series, viewed from the right-hand side. Coronal apices 
of all except the posterior tooth have been broken away. Reproduced from a 
photograph by Mr. C. H. Currier without retouching. Original preserved in the 
Museum of Comparative Zodlogy at Cambridge, Mass. (Cat. No. 749). x 3. 
PLATE 3. 
Fig. 1. Campodus variabilis (Newb. and W.). Coal Measures; Osage County, 
Kansas. Oral aspect of same specimen shown in Plate 2, with the 
anterior extremity shown uppermost. X 2. 
Fig. 2. Ctenacanthus venustus, sp. nov. Kinderhook limestone; Iowa (2). Lateral 
aspect of spine referred to the anterior dorsal fin, and belonging to an 
immature individual. Original preserved in the United States National 
Museum at Washington. (Cat. No. 3385). x }. 
PLATE 4. 
Campyloprion annectans Eastm. Carboniferous or Permo-Carboniferous ; locality 
unknown. Symphysial dentition, showing portions of about 20 fused teeth, 
viewed from the left-hand side. Reproduced from a photograph by Mr. C. H. 
Currier without retouching. Original preserved in the Museum of Comparative 
Zoology at Cambridge, Mass.  X 2. 
