202 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
Deltodus contortus (St. Joun and WorrTuHEN). 
(Plate 4, Figs. 37, 43.) 
1883. Taeniodus contortus St. John and Worthen (ex L. G. de Koninck MS.), Pal. 
Illinois, Vol. VIL., p. 76. 
Type. — Posterior dental plate ; Museum of Comparative Zodlogy. 
‘The genus Taeniodus, with the type species of T. contortus, was held by its 
founders to be closely related to Psephodus, from which it was stated to be 
chiefly distinguished “by the pronounced differentiation of the coronal con- 
tour.” Three species from the Mississippian series, besides the type, which is 
from the Lower Carboniferous of Belgium, were included under this genus by 
the original authors, but are distributed by A. S. Woodward in his Catalogue 
of Fossil Fishes between the genera Psephodus and Deltodus. We must ex- 
press our complete concurrence with Dr. Woodward’s views, and in order that 
others may judge of what the type species of Taeniodus is like, we here figure 
it for the first time, and would call attention to the close resemblance between 
it and the species of Deltodus illustrated in Plates IX. and X. of the seventh 
volume of the Illinois Palaeontology. These forms are interesting in that they 
show very distinctly the outlines of the individual teeth of which the large 
principal dental plates are composed. 
Formation and Locality. — Lower Carboniferous limestone ; Visé, Belgium. 
POHCILODUS MCoy. 
This genus is peculiar in having the two posterior series of teeth in each 
jaw fused into a single much enrolled plate, the coronal surface of which 
is marked by more or less distinct transverse ridges and furrows. St. John 
and Worthen supposed that plates of this character pertained solely to the 
upper jaw, and regarded the triangular plates commonly referred to the genus 
Deltoptychius as constituting the lower dentition of Poecilodus. This idea, 
however, is not shared by any subsequent writers, and there is abundant evi- 
dence to show that the dentition of each jaw of Poecilodus was transversely 
ribbed. Accordingly, the species described by St. John and Worthen as 
“ Poecilodus springert”’ and P. worthent, in the seventh volume of the Illinois 
Palaeontology, are properly transferred to the genus Deltoptychius of Agassiz. 
Poecilodus rugosus Newserry and WorrtHEN. 
1866. Poecilodus rugosus Newberry and Worthen, Pal. Illinois, Vol. II., p. 94, 
Pl, VIL; Fig. 13: 
1866. Poecilodus ornatus Newberry and Worthen, Jbdid., p. 95, Pl. VIII., Fig. 14. 
1883. Chitonodus rugosus St. John and Worthen, Op. cit., Vol. VII., p. 112, 119. 
The specimens at the command of Newberry and Worthen at the time of 
their original description of this species were very fragmentary, and more per- 
