WILLISTON : A NEW SPECIES OF SAGENODUS. 177 



Sagenodtcs occide^ytalU Newberry. Rep. Geol. Surv. III., ii, 19 [Rhizodus); 

 Cope, Proc. Amer. Phil. Soc, xxxvi, 75. Mazon Creek shales. 



Sagenndus reticidnfufi Newberry. lb. 60; iv, 349, pi. iii, f. 9 {Ctenodua); 

 Cope, Proc. Amer. Phil. Soc, xxxvi, 1897, 78, pi. i, ff. 2, 3. Coal Measures, 

 eastern Illinois. 



Dental plate 30 mm. in length, with seven low, radiating ridges ; 

 the whole crown of the teeth exhibits a fine, reticulate ornamentation, 

 which, on the ridges, is more or less radiate, and has the appearance 

 of hachures. 



The following species are known only from the scales, while nearly 

 all of the foregoing are known only by the teeth, usually a single 

 crown. I reproduce Cojae's table (Proc. Amer. Phil. Soc, xxxvi, 77, 

 1898) of nearly all those species based upon scales: 



1. Concentric lines conspicuous 2 



No concentric lines 4 



2. Tessellation and radii not conspicuous; scales medium to large, subround, 



oeeidentalis. 

 Concentric lines fewer, marginal ; tessellation conspicuous, radiating from 

 a center 3 



3. Scales medium to large, acuminate distad; tessellation very fine. . . foliaiiis. 

 Scales small to medium, elongate, subacuminate; tessellation elongate, 



without regular radii or concentric ridges; center at extremity 



reticulatus. 



Scales medium to large, parallelogrammic ; tessellation radiating, radii and 



concentric ridges extending to free edge ; center at end 



conchiopsis (conchiolejiis). 



Scales very large, elongate; tessellation confined to center, from which is- 

 sue numerous, well- spaced radii lacovianus. 



Scales medium, truncate; tessellation coarse, diamond-shaped, quincunci- 

 ate qidncunciatus. 



Scales medium, truncate; tessellation coarser, parallelogrammic . . brownice. 



4. No concentric lines or center; a border of fine radii. Very large, elongate; 



tessellation very fine magister. 



No concentric lines or radii; tessellation extending to posterior border. 

 Scales deep, smaller ; center submedian ; tessellation of medium coarse- 

 ness gurleianus. 



Sagenoduft foliatus Cope, Proc. Amer. Phil. Soc, xxxvi, 77, 1897, pi. i, f. 1. 

 Mazon Creek shales. 



Sagenodus conehiolepis Cope, ib., 79, pi. i, f. 4. Mazon Creek shales. 



Sagenodus lacovianus Cope, ib., 79, pi. i, f. 5. Mazon Creek shales. 



Sagenodus quineunciatus Cope, ib., 80, pi. i, f. 6. Mazon Creek shales. 



Rhizodus reticulatus Newberry, Geol. Surv. 111., iv, pi. iii, ff. 13, 14. 



Sagenodus brotvnice Cope, ib.. 81, pi. i, f. 7. Mazon Creek shales. 



Sagenopus ^nagister Cope, ib., 81, pi. i, f. 8. Mazon Creek shales. 



Sagenodus gurleianus Cope, ib., 82, pi. i, f. 9 [nomen bis lecium).* Mazon 

 • Creek shales. 



Sagenodus quadratus Newberry (fide Cope 1. c) 

 * Sagenodus ; Hay, Amer. Nat. 



