366 The American Geologist. June, 1895 
tainty and comparative uselessness of such definitions will at 
once appear when, as in the case of a still undescribed speci- 
men in Dr. Clark's collection, three forms of tooth are seen in 
the same mouth, of which two only are truly cladodont. Ob- 
viously no description resting solely on the form of a tooth 
can be maintained for any other object than for that tooth 
itself. As names for the fishes that carried the teeth they 
must evidently be very uncertain unless we can determine the 
fish to which each belonged, and this, in the light of the 
above fact, will never be in all cases possible. And even 
where it can be done it will be more philosophical to refer the 
tooth to the fish than the fish to the tooth. 
Cladodent teeth are very abundant especially in Carbonif- 
erous strata such as the Lower Carboniferous limestone of 
Illinois and Indiana and tlie Mountain limestone of England, 
but, with the exception of the specimen described by Dr. Tra- 
quair and perhaps one or two others, all very imperfect, we 
had until- the Cleveland fossils came to light no knowledge of 
the fishes themselves. 
3. Fins. — These present a few points deserving of note. In 
the first place the pectoral fins exhibit very coarse raj^s in the 
anterior portion and as far as the middle, behind which point 
they become finer to the posterior extremity. There is a dis- 
tinct membranous border crossed by numerous excessively fine 
raylets or trichinosts. The number of rays seldom varies 
much from twenty and there is little forking, except in the 
smaller ones, though intermediate, secondary and even terti- 
ary rays appear toward the margin, either in consequence of 
a duplication through crowding or the persistence of a second 
and third row whose bases have been suppressed for want of 
room. It is very difficult in the specimens that I have exam- 
ined to see any trace of the "archipterygial" form of fin, as 
defined by Gegenbaur. The fin presents a decidedly icthyop- 
terygial form, at least outside of the body, the rays extending 
continuously from the body line to the tip. Whatever struc- 
tures existed within the body as a pectoral girdle are too in- 
distinct in the crushed condition of the fossil to be positively 
identified. Possibly other specimens may exhibit these parts 
more clearly in the future, but the interpretration of the con- 
