92 Mr. T. Stock on the “Kammplatten”’ or 
The series which Prof. Fritsch figures* is probably incom- 
plete. From the figure it would appear that it was single; 
but in his descriptiont he says that it is double, consisting of 
three elements on each side facing each other. In the figure, 
too, the edges of the plates appear to be crenulated rather than 
pectinated—an appearance which must be due to fracture, if 
the detached plates which he figures really belong to the 
same species. I must confess that I do not feel satisfied on 
that point. If his figure 6 really represents any considerable 
fragment of this problematical apparatus, it seems to me that 
it would be safer to take that as a guide to the limitations 
of specific diagnosis than to attempt to graduate into each 
other from scattered evidence plates so divergent as those 
represented, for example, by his figures 2,9, and 10. Of 
course, without seeing the actual specimens and the whole 
of Prof. Fritsch’s excellent material, it would be unsafe to 
speak very confidently on the matter ; but after an attentive 
study of his descriptions and figures, and after examining 
the British specimens, I should be inclined to think that 
his figures 2, 8, and 13 represent one series, his figures 6 and 
perhaps 9 another, and his figure 10 possibly a third. At any 
rate, if the whole of these are to be referred to a single cate- 
gory, I cannot see any reason for excluding his figures 11 and 
12 from the same category. The divergence is no greater ; 
yet he considers that they represent a distinct species. 
Three additional species of Ophiderpeton are described 
from other evidence; and there seems proof of the existence of 
a fourth. This fact alone might have warranted, one would 
have thought, a freer separation of the “ Kammplatten”’ into 
forms of specific equivalence. 
If the series referred to is taken as a guide to the in- 
vestigation of the value of specific characters, it will be 
seen that the amount of variation is slight between the con- 
stituent elements. Shght differences of form, accompa- 
nied by differences in size and in the number of the pectina- 
tions, are all the variation that can be detected. The 
difficulty, however, is increased in detached specimens by the 
different aspect presented as they are seen on their concave or 
convex surface. Sometimes they le on their side with the 
pectinated edges buried in the matrix; and many of them 
appear to have undergone distortion. The British forms that 
I have been able to examine appear to be distinct from those 
discovered in Bohemia. All the forms that I have seen may 
be referred to three, or more probably four, distinct series ; and 
* Op. cit. pl. xx. fig. 6. + Op. cit. p. 122. 
