652 E. B. BRANSON 



found. There are holodont teeth in abundance in the phosphate 

 bed that bears D. mercurii, but there seems to be no way of asso- 

 ciating them with the Deltodus teeth. 



In 1905 the writer differentiated Sandalodus from Deltodus on 

 the basis of the theory that the former had only one tooth to each 

 ramus of the jaw and the latter three. 1 The present investigation 

 indicates the correctness of the conclusion that Sandalodus had 

 only one tooth in each ramus, but this was a maxillary tooth, and 

 the Deltodus teeth are mandibular of the same species. One of the 

 evidences given by Branson that Deltodus had three teeth to each 

 ramus was the truncated or grooved anterior edge of the median 

 teeth, adapted for articulation with other teeth. The restoration 

 here given shows the median teeth articulating with each other 

 and dispenses with the probability that there was a third tooth 

 in each ramus. It is probable that the dentition of forms described 

 from the Mississippian of the interior may be reconstructed, and 

 the writer intends to attempt such reconstruction. 



The restoration presented in PL VI, Figs. 1-3, is the result of 

 the study of a large series of teeth and is believed to be approxi- 

 mately correct. 



The right maxillary tooth is modeled and the left is perfect. 

 The right outer mandibular has the outer end restored and the 

 left inner mandibular is restored at the outer end. The extent of 

 restoration is easily determined in the photograph. Fig. 1, showing 

 the upper and lower dentition apposed, probably represents the 

 back end of the jaws, and the teeth were probably deeply inserted. 



Cladodus occidentalis Leidy (PL II, Figs. 23 and 24) 

 1859. Cladodus occidentalis Leidy, Proc. Acad. Nat. Sci. Phila., p. 3. 

 1866. Cladodus mortifer Newberry and Worthen, Geol. Surv. III., II, 22, PL I, 



Fig. 5- 

 1870. Cladodus mortifer St. John, Proc. Am. Phil. Soc, XI, 431. 



1872. Cladodus mortifer St. John, Final Kept. U.S. Geol. Surv. Nebr., p. 239, 

 PL III, Fig. 6; PL VI, Fig. 13. 



1873. Cladodus occidentalis Leidy, Rept. U.S. Geol. Surv. Territ., I, 311, PL 

 XVII, Figs. 4-6. 



1897. Cladodus mortifer Newberry, Trans. N.Y. Acad. Sci., XVI, 285, PL 



XXII, Fig. 2. 

 1903. Cladodus occidentalis Eastman, Bull. Mus. Comp. Zool., XXXIX, 168, 



PL II, Figs. 3, 8, and 9. 



1 E. B. Branson, Jour. Geol., XIII, 26. 



