No. 380.] DEVONIAN PTYCTODONTID£. 549 
relationships, and the structure is all but obliterated in the 
half-tone reproduction. This much, however, we are warranted 
in saying: the extreme tip of the beak has been broken, and 
the bony substance about it extensively worn away, but traces 
remain of a thin bony splint or prolongation, somewhat triangu- 
lar in outline, attached to, and extending in front of, the beak. 
The ossification is apparently continuous with that of the 
dental plate itself, yet has not nearly the thickness of the 
symphysial surface, being seemingly confined to the inner face 
thereof. Theoretical objections certainly will not allow us to 
conceive of the existence of an anterior azygous tooth, nothing 
of the sort being known to occur in this family ; nor can 
the structure justly be called adventitious, since one of Mr. 
Monroe’s specimens presents a similar, yet equally baffling 
appearance. The only plausible conjecture we can form 
regarding it is that, owing to the large size of the dental plates, 
some other besides merely cartilaginous means was required to 
strengthen their union at the symphysis, and this was supplied 
by an ossification arising from the inner side of the dental 
plates, forming a sort of bony suture. Mention is made of this 
anomaly in the hope that future discoveries may lead to its 
adequate explanation. 
P. predator sp. nov. (Fig. 43). — The type specimen shown 
in the foregoing figure (p. 483) is unique. It formsa part of the 
Schultze Collection belonging to the Museum of Comparative 
Zoology, and was found in the Devonian limestone near Gerol- 
stein, in the Eifel District. It is of no little interest to note 
that the three Ptyctodont genera, although represented by 
vicarious species, should thus occur together in homotaxial 
deposits of such widely separated regions as Central Europe 
and the Mississippi Valley. 
Unfortunately, the present solitary specimen is not very well 
Preserved, but still enough remains to show its general form 
and relationships. The part exposed to view is the anterior 
portion, happily with the beak intact, of the right lower dental 
plate. The inner surface is concealed by the matrix, and, being 
partly abraded, it is not easy to determine the original thickness 
of the tooth. Evidently the triturating surface was wide, rela- 
