488 On the Fossil Fishes of the Carboniferous Limestone Series of Great Britain. 
teeth amongst recent or fossil fishes, a striking resemblance in some respects is 
observed between it and the fossil genus Janassa of Miinster—(Beitrige zur Petre- 
factenkunde, Heft V., p. 38, et seq.) Messrs. Hancock and Atthey have pointed out 
the identity of Janassa with Climaxodus (M‘Coy) in the “ Nat. Hist. Trans. of North- 
umberland and Durham,” vol. iii., p. 330. The teeth of both genera are described 
as generically identical, “the differences being only those of proportion, there 
being not a single character of importance to distinguish one from the other.” 
“The teeth are depressed and elongated in the antero-posterior direction, and lapse 
a little backwards. In form there is a wide concave margin, which standing up, 
like a scoop or dredging bucket, is the cutting edge. Behind this the surface is 
covered with transverse imbricated ridges, forming the grinding or crushing 
portion ; and further down, on a lower plane, the broad depressed root projects 
backwards and downwards for a considerable distance. In profile they present a 
sigmoid curve, the frontal scoop-like portion standing up in the direction of the 
oral cavity, the posterior or root-extremity being turned downwards in the oppo- 
site direction.” Both genera are described as possessing two kinds of teeth. 
“Those already indicated may be looked upon as the principal or primary dental 
organs; the other kind, or the secondary, in the two genera resemble each other 
just as closely as do. the primary ; and it is interesting to find that these secondary 
teeth agree pretty closely with some of those included in the genus Petalodus of 
authors, only they are oblique. The association of these Petalodontoid teeth with 
the primary ones is too obvious to be called in question.” In Janassa the two 
forms are actually found arranged in order, side by side, both in the British and 
German specimens. The latter are from the magnesian limestone, the former from 
the coal measures and mountain limestone. 
The teeth are described as being arranged in the mouth “in slightly arched 
transverse rows, the largest symmetrical primary tooth being situated on the 
median antero-posterior line, and projecting a little in advance of the others, on 
each side of this there are two similar teeth, but somewhat less, the outside one 
being twisted obliquely ; the row is then terminated on either side by one of the 
Petalodontoid form. There are therefore seven teeth in each row, including both 
kinds—five primary, two secondary. Mitnster represents five or six rows in close 
succession from back to front, the teeth and rows gradually diminishing in size 
forward. It is evident, then, that the arrangement of the buccal armature more 
closely resembles that of the rays than the cestracionts or the sharks ; and indeed 
notwithstanding the difference in the teeth themselves, in their nptommetent they 
agree In a remarkable manner with those in Mylobatis aquila and Zygobatis 
Mar ginata—a, relationship which was recognized by Agassiz. The largest teeth 
are 12 inch in length, including the root, and § inch wide at the broadest part. 
Smaller side teeth are not more than $ inch long and the petalodont secondary 
teeth about 2 inch in length. The crown is fully two-thirds the entire length 
