196 . BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



Phoebodus dens-neptuni, sp. nov. 



(Plate 4, Fig. 39.) 



Type. — Detached tooth ; Museum of Comparative Zoology. 



Teeth of moderate size, with three principal cones less than one cm. in 

 height. Median cone erect, gradually tapering, lateral cones of unequal 

 height, gently curved outward toward the apex ; all three delicately striated, 

 subcircular in cross-section, the median broader than the others. 



This species is founded upon a unique tooth from the Keokuk limestone of 

 Iowa, which seems to be intermediate in character between the so-called Diy- 

 loclus incurvus and D. duplicatus of Newberry and Worthen accompanying it in 

 the same horizon. From the former it is distinguished by its more slender 

 form and striated cones, and from the latter by its possession of three principal 

 cones instead of four, as in that species. The nature of the base is not deter- 

 minable from the solitary example that is known of the present species. 



Formation and Locality. — Keokuk limestone ; Keokuk, Iowa. 



COCHLIODONTIDAE. 



A deal of confusion exists regarding the nomenclature of certain species of 

 Sandalodus, Deltodus, and Deltoptychius occurring in the Carboniferous rocks 

 of the Mississippi Valley, a state of affairs which is attributaltle to the imper- 

 fect preservation of the greater number of their remains. A study of a large 

 collection of Cochliodont teeth belonging to the Museum of Comparative 

 Zoology and the United States National Museum has suggested the following 

 synonymy in the case of several disputed species. 



SANDALODUS Newberry and Worthen. 



Sandalodus laevissimus Newberry and Worthen. 



(Text-figure 11.) 



1866. Sandalodus laevissimus Newberry and Worthen, Pal. Illinois, Vol. II., p. 104, 



PI. X., Figs. 6-8. 

 1866. Sandalodus grandis Newberry and Worthen, Ibid., p. 105, PL X., Fig. 9. 

 1866. Deltodus grandis Newberry and Worthen, Ibid., p. 101, Pi. IX., Fig. 9. 

 1866. Cochliodus ? crassus Newberry and Worthen, Ibid., p. 91, PI. VIII., Fig. 2. 

 1866. Psammodus ? semicglindricus Newberry and Worthen, Ibid., p. 109, PI. XL, 



Fig. 4. 

 1866. Psammodus ? rhomboideus Newberry and Worthen, Ibid., p. 110, PI. XL, 



Fig. 6. 

 C?) 1879. Deltodus grandis J. S. Newberry, Ann. Rept. Geol. Surv. Indiana, 1876- 



78, p. 844. 



