73 
A STUDY IN VARIATION : 
PUGNAX PUGNUS (Martin) and PUGNAX cf. 
SULCATUS (J. de C. Sow). 
BRIAN SIMPSON, M.Sc., UNIVERSITY COLLEGE, SWANSEA. 
( Continued from page 61 ) . 
The most obvious variants are depth and thickness, for the 
tumidity or thinness of the specimens is readily seen. The 
relation X too is seen in Fig. 3 C, and again the 
largest number of specimens lies within narrow limits 50 per 
cent. — 70 per cent, and includes the mature specimens, 
while the larger specimens approach 100 per cent, with the 
depth and breadth nearly equal ; such specimens are very 
tumid as seen in Fig. 2. The mean is 61.48 and the arithmetic 
« 60 65 TO 75 60 35 90 95 
Fig. 4a. 
mean of the deviations is 8.62 or 12.39 P er cent, of the mean. 
These figures are low and &S would be expected are* very near 
those of the succeeding factor t K ick Li e Jj x 100. Here the 
range is high, being 41 per cent., and contrary to the other 
variants the specimens are not confined within narrow limits, 
m 
Mo ) 
1933 April 1 
D 
