198 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



Sandalodus complanatus (Newberry and Worthen). 



1866. Deltodus complanatus Newberry and Worthen, Pal. Illinois, Vol. IL, p. 98, PI. 



IX., Fig. 4. 

 1866. Trigonodus major Newberry and Worthen, Ibid., p. 112, PI. XL, Figs. 3, 9. 

 1870. Deltodus complanatus Newberry and Worthen, Ibid., Vol. IV., PI. III., Figs. 



5,8 (and 12?). 

 1883. Sandalodus complanatus St. John and Worthen, Ibid., Vol. VII., p. 184, PI. 



XII., Figs. 1-4. 



Much discussion has arisen as to whether the fragmentary teeth described 

 as " Deltodus complcmatus " are truly referable to that genus, or belong to San- 

 dalodus. A study of a considerable amount of material from the Burlington 

 Group has convinced the writer that the above synonymy, which is taken 

 from St. John and Worthen, is correct, and that the teeth figured as D. com- 

 planatus in the posthumous paper of Newberry i are fragments of D. occide^italis 

 N. and W. 



DELTODUS Agassiz. 



Two species of Deltodus are found in mutual accompaniment throughout 

 both the Burlington and Keokuk divisions of the Mississippian, and although 

 their extreme forms are quite distinct (Plate 4, Figs. 38, 42), they are connected 

 by intermediate gradations (Plate 5, Fig. 53), so that in the case of fragmentary 

 teeth it is sometimes difficult to determine which of the two species is repre- 

 sented. Generally speaking, the teeth from the Burlington limestone are less 

 perfectly preserved than those from the Keokuk, and chiefly for this reason the 

 synonymy has become more or less involved. We propose to recognize the 

 two forms under the names of D. spatulatus Newb. and Worth, and D. occiden- 

 talis (Leidy) respectively. The first-named ranges from the Kinderhook to 

 the Keokuk inclusive, and the latter from the Burlington to the St. Louis 

 Group, being particularly abundant in the Keokuk and Warsaw beds. 



Deltodus spatulatus Newberry and Worthen. 

 (Plate 4, Figs. 41, 42; Plate 5, Fig. 5.5) 



1866. Deltodus s/>atidalus Newberry and Wortlien, Pal. 111., Vol. II., p. 100, PI. IX., 



Fig. 7. 

 1870. Deltodus spatulatus Newberry and Worthen, Op. cit., Vol. IV., PI. III., Fig. 



11. 

 1870. Deltodus alatus Newberry and Worthen, Ibid., p. 368, PI. II., Fig. 6. 

 1870. Cochliodus costatus {jxirs) Newberry and Worthen, Ibid., p. 364, PI. III., Fig. 



12 {non Fig. 10). 

 1879. Deltodus spatulatus J. S. Newberry, Ann. Rept. Geol. Surv. Indiana, 1876-78, 



p. 346. ' 



1 Trans. N. Y. Acad. Sci., Vol. XVI., 1897, p. 298, PI. XXIV., Figs. 1-7. 



