EASTMAN: CARBONIFEROUS FISHES FROM THE CENTRAL WESY. 201 
with D. spatulatus. In Plate 4, Fig. 38, is shown a very perfect posterior 
dental plate of the typical form, rather under the average size. Some very 
large examples have a width along the antero-lateral margin of nearly 6 cm., 
and in these much worn teeth the coronal contour is decidedly flatter than in 
immature specimens. 
Messrs. Newberry and Worthen have figured the supposed anterior dental 
plate belonging to this species,! but the specimen appears to be too strongly 
enrolled for coadaptation with the antero-lateral margin of the posterior dental 
plate, and the same criticism applies to the specimen referred by St. John and 
Worthen 2 to a corresponding position. There is no record of the two prin- 
cipal dental plates of this species ever having been found in natural associa- 
tion, and it will require the careful study of much additional material before 
we can be fully satisfied as to the characters of the anterior components of the 
dentition. It is to be noticed that the initial coiling is much less marked in 
the teeth of this species than in most forms of Deltodus and Sandalodus, 
Formation and Locality. — Burlington, Keokuk, Warsaw, and St. Louis 
Groups; lowa and Illinois. 
Deltodus costatus (Newserry and WorrHey). 
1870. Cochliodus costatus Newberry and Worthen, Pal. Illinois, Vol. IV., p. 364, PI. 
IIL, Fig. 10 (non Fig. 12). 
1883. Cochliodus costatus St. John and Worthen, Op. cit., Vol. VII., p. 167. 
This species has not been previously reported from a higher horizon than the 
Burlington division of the Mississippian, but several examples from the Keokuk 
limestone are preserved in the United States National Museum and in the 
collections belonging to the State University of Iowa. Very similar teeth also 
occur in the Warsaw beds, and have been described as Deltodus trilobus by St. 
John and Worthen.® <A tooth of the same general nature is also referred by 
the same authors to D. occidentalis, and is supposed by them to represent the 
anterior dental plate belonging to that species.* It is evident that the Warsaw 
forms last referred to are anterior dental plates, but attempts to correlate them 
with the posterior dental plates of other known forms are necessarily attended 
with great uncertainty. 
Formation and Locality. — Burlington and Keokuk Groups ; Iowa. (? War- 
saw beds ; Illinois.) 
1 Pal. Illinois, Vol. IL., 1866, Pl. IX., Fig. 3. 
2. Itid., Vol. VII., 1883, Pl. IX., Fig. 10. 
3 Ibhid., Vol. VII., 1888, p. 148, Pl. IX., Fig. 8. 
4 Pal. Illinois, Vol. VIL, 1883, Pl. [X., Fig. 10. (Warsaw limestone ; Warsaw, 
Illinois.) 
