92 DEAN. [Vot. IX. 
are resolvable into a double row of cartilage rods; their 
structure is the outcome of their living conditions. He thus 
concludes that Cladoselache, if not falsely restored, would be 
a typical selachian, possessed of all the essential peculiarities 
of its later kindred. 
Before these contradictory views may be considered, the 
structure of the paired fins should be re-examined in the light 
of the newly-discovered material. 
The pectoral fin (Fig. 1) is remarkable in that its broad base 
is continuously attached to the body, and that its plane is in 
the moving direction of the fish. It is a flat triangular 
plate, directed outward and slightly downward. There can 
be no doubt that the web-like posterior fin margin was 
continuous with the trunk integument, and that there was no 
projecting tip of a lateral Stammstrahl such as Fritsch has 
figured in the ventral of Pleuracanthus, or such as Traquair '4 
has described in the pectoral of Cladodus. The figure shows 
clearly the row of parallel cartilaginous rods remarked by 
Woodward, that appear to take their origin in the outer body 
wall and proceed directly to the outer fin margin, unjointed. 
The rays may, for convenience, be divided into three groups of 
about ten each,—fore, middle, and aft, which in structure 
grade imperceptibly one into the other. The first group is 
of stout bars of cartilage, and includes about half of the fin; 
its foremost ray is the stoutest, shortest, is directed forward; 
and the following rays, increasing in size and compacting 
together, form the stout anterior margin of the fin. The 
middle rays are the longest, tapering and often forking at 
the tips. The rays of the final group are narrower, slenderer, 
and more forked; they decrease in size, becoming more and 
more posteriorly directed. Noteworthy is the clustering 
process which these rays appear to be undergoing, as pointed 
out by Smith Woodward ; their bases are so tightly crowded 
together that the rays have been obliged to form a dorsal and 
a ventral set, as may be clearly seen at the distal end of the 
fin where the flattening has given room for the tips of the 
alternate rays to assume their position in a single plane. The 
strength of this compact structure is noteworthy ; clustered 
