18 
GRAPHIC COMPARISON OF GENERA AND SPECIES 
Professor Swinnerton has recommended a more extensive and system- 
atic use of graphs in palseontology. For illustration of the difference in 
development in regard to thickness of Cadoceras and Paracephalites the 
graph method is excellent. It is extended for making comparisons in 
certain other cases, using the following data: 
Diameter 
Thickness, 
per cent 
A 
Paracephalites jucundus 
34*0 
65-0 
46-0 
65*0 
A* 
“Macrocephalites” pila Nikitin 
34*0 
77-0 
(PI. X, f. 45) 
60*0 
77*9 
B 
Paracephalites gktbreeceng , 
36*0 
47*5 
50-0 
50-0 
65*0 
55-0 
920 
50*0 
101*0 
47*0 
C 
Metacephalites metastatus . . . . . . 
30*5 
46-0 
(Body-chamber) 
43*5 
48*0 
D 
Miccocephalites laminatus 
15*0 
45*0 
20*0 
42-5 
E 
Miccocephalites concinnus 
12*0 
44*0 
19*5 
40-0 
F 
Catacephalites durm. 
33*0 
72*0 
44*0 
65*0 
G 
‘ ‘Am. ( Macrocephalites j’ * ishmae. .... 
20*5 
73-0 
Newton (PI. XL, f. 2) 
34*0 
70-0 
59*0 
66-0 
H 
“Am. (Macroc.)” ishMaev ar. arcticus 
38*5 
64*0 
Newton, PI. XL, f. 1 
66 0 
53-0 
I 
“Am. (Macroc.)” ishmae . .... ..... . ........... 
22*5 
52-0 
Newton, Pi. XL, f. 3 
43-0 
49*0 
67-0 
52*0 
J 
Cadoceras suhlaeve 
20*5 
52*0 
a topotype 
37*0 
59-0 
57*0 
77*0 
J a 
Do. another example 
47*0 
58*0 
a topotype (S. Buckman, 4), PI. CCLXXV 
65*0 
80*0 
Jb 
Cadoceras modiolare Nikitin. . .... ... ... 
29*5 
44*5 
Estimates from his drawing (Fig. 1, p. 53) and his text (p. 52} 
45*0 
62*0 
assuming his fig. is reduced X 0*76 
73-0 
82-0 
111*0 
90*0 
150-0 
97*0 
K 
Cadoceras wosnessenski 
27*0 
41*0 
Pompeckj (2, text p. 252) 
48-0 
56*0 
L 
“ Cadoceras ” grewingki 
8-0 
56*0 
Pompeckj, text and fig. 
12*0 
50*0 
17*5 
40*0 
32*0 
40-0 
37-0 
40*0 
