EASTMAN : CARBONIFEROUS SHARKS. 69 
in Campodus may to all intents and purposes be considered as teeth, which 
probably formed a mosaic-like pavement. It would appear very doubt- 
ful, however, if these outgrowths of dentine in the present specimen ever 
functioned as teeth, although they may have served as a sort of cingu- 
lum ; and their origin is probably attributable to an excessive supply of 
dentine-forming material, which was deposited adjacent to the larger 
series. That they are closely related to the principal teeth is evident 
from the fact that they partake of the same curvature toward the front 
as these. One of the distinguishing characters of Karpinsky’s genus 
consists in the presence of a double groove extending along the lateral 
faces of the crown near the base. Nothing of this nature appears in the 
present example, nor in either of the other species of Campyloprion. 
The last point we have to consider is the base, by which is meant the 
mass of vasodentine that served as a common support for the series. 
Just as the teeth are fused into a continuous series, and their extremities 
pass by insensible gradations into a common base, so the latter may be 
said to correspond, in part, at least, to fused roots. We say “fused,” for 
the reason that no traces of segmentation are visible: a condition which 
is also true of Helicoprion, but not of Edestus, although in the latter 
genus the basal segments are sometimes obscure. As in the other species 
of Campyloprion, and also in the completely coiled genus, the base is 
channelled below by a longitudinal canal of considerable size. ‘The dimen- 
sions and form of cross-section of this channel appear to have been about 
the same as in C. davisit and Helicoprion bessonowi, although compari- 
sons are difficult, owing to mechanical compression and partial removal 
of the lateral walls. Longitudinal striz extending along the base, and 
also a generally perforated appearance, such as are here in evidence, are 
characters not uncommonly presented by the roots of sharks’ teeth, and 
are correlated with the attachment of the series in the supporting sym- 
physial cartilage. The enormously developed basal segments (roots) 
of Edestus exhibit a more vascular structure than the compact vasoden- 
tine base of Campyloprion. 
Comparison of Genera possessing an Hdestus-like form of 
Dentition. 
The principal characters of the four genera of Cestraciont sharks 
whose dentition has been described in the preceding pages, may be 
summarized as follows : 
VOL. XXXIx.— NO. 8 2 
