198 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 
Sandalodus complanatus (NEwBerRy and WorTHEN). 
1866. Deltodus complanatus Newberry and Worthen, Pal. Illinois, Vol. II., p. 98, Pl. 
IX., Fig. 4. 
1866. Trigonodus major Newberry and Worthen, Jdid., p. 112, Pl. XI, Figs. 3, 9. 
1870. Deltodus complanatus Newberry and Worthen, Jbid., Vol. IV., Pl. IIIL., Figs. 
5, 8 (and 12 ?). 
1883. Sandalodus complanatus St. John and Worthen, Jbid., Vol. VIL, p. 184, Pl. 
XII., Figs. 1-4. 
Much discussion has arisen as to whether the fragmentary teeth described 
as “* Deltodus complanatus”’ 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! are fragments of D. occidentalis 
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 5yFig. 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-enamed 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 Newserry and WorrTHEN. 
(Plate 4, Figs. 41, 42; Plate 5, Fig. 55.) 
1866. Deltodus spatulatus Newberry and Worthen, Pal. Ill., Vol. II., p. 100, Pl. IX., 
Fig. 7. 
1870. Deltodus spatulatus Newberry and Worthen, Op. cit., Vol. IV., Pl. IIL, Fig. 
1 
1870. Deltodus alatus Newberry and Worthen, Jbid., p. 368, Pl. IL, Fig. 6. 
1870. Cochliodus costatus (pars) Newberry and Worthen, Ldid., p. 364, Pl. IIL, 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, Pl. XXIV., Figs. 1-7. 
