The Use of Graphs in Paleontology. 401 
different measurements may pe made, but only those which reflect 
distinct changes have been taken into account here. They are the 
following :— 
(A) The percentage number of septa that have become distinctly 
radial in their arrangement. In addition to lying along a radius, 
this imphes that they are equal in length. 
(B) The number of minor septa expressed as a percentage of the 
total number of major septa. 
(C) The reduction of the fossule. 
(D) The percentage number of septa in the counter cardinal 
quadrants. 
(E) The number of septa as a percentage of the total number in 
the adult. 
(F) The diameter of the central Space occupied by the septa. 
(A) to (D) relate chiefly to changing symmetry. 
(F’) reflects both the progressive extension of the central area, 
which becomes occupied by tabule alone, and a gradual shortening 
of the septa themselves. 
FIG. 8.—A series of graphs representing stages in the development of 
Caninia cornucopia. 
In Fig. 8 the line b represents the measurements on Mr. Carruthers’ 
fig. 1b. This was the earliest stage in development described by him. 
The other lines correspond to his figs. le to 17 respectively. 
It is at once evident that the graphs, though they are not parallel, 
develop out of one another in Sequence ; that is to say, that with 
one slight exception they do not cross one another. The slight 
exception is the crossing of g and j between Hand F. In the absence 
of later stages than Jj it is impossible to explain this. It may be 
due either to a reversal of the direction of development, or to that 
fluctuation about a mean which characterizes an element that has 
VOL. LVIII.—NO. Ix. 26 
