82 
Dr. Gregory^ on the Post-tertiary 
acute angle. They stop sliort_, however_, of the length of the 
secondary rays^ as these do of the primary_, and to about the 
same extent^ each line_, as we go from the secondary towards 
the primary rays^ becoming shorter than the preceding one_, 
till the third and last on each side is reduced to four or five 
dots, and there are often seen_, in the larger discs_, after the 
fourth of these parallel lines, one or two dots, indicating the 
presence of a fifth, for the extension of which no room has 
been left. 
It is evident that so remarkable a structure must amount to 
a specific, at least, if not to a generic distinction. It will be 
observed that the successive shortening of the lines, from the 
centre towards the circumference, produces a good many 
blank spaces, which, however, are so symmetrical, as not to 
catch the eye as blanks, as the blanks in Half six do, which, 
besides being irregular as to position, are smaller and more 
numerous. Nevertheless, although I have not yet had time 
to examine E. Ralfsii minutely, I rather think that its struc- 
ture is, essentially, like that of E. sparsus, although in E. 
Ralfsii the dots are both larger and more closely set. Whether 
this be the only cause of the blue colour I cannot say; but I 
find that individuals of E. sparsus, in which, as already stated, 
the rays and dots are very close, still retain their brown 
colour, only darker. It is possible that the blanks in E. 
Ralfsii may prove, when closely examined, to be the result of 
the structure above described, when the rays and dots are 
close ; yet this does not explain how E. sparsus should often 
occur, both when sparsely and closely marked, without any 
of the peculiar blanks of E. Ralfsii. The individual here 
figured, probably from its smaller size, and especially from 
the sparseness of the markings, is colourless ; while, as I have 
stated, E. sparsus is usually of a paler or darker brown. 
I presume we shall have a description of E. Ralfsii, and 
probably of its varieties, in vol. ii of the ' Synopsis.^ In the 
meantime I venture to direct the attention of observers, both 
to the very remarkable structure so well seen in fig. 47, and to 
the differences in colour and other points between E. sparsus, 
and what is generally believed to be E. Ralfsii, although I am 
inclined to believe that both forms possess the same general 
structure, and the same arrangement of the markings. (299.)^ 
* On comparing again several discs of both kinds, I find that the arrange- 
ment is the same in both, but that in those of E. Ralfsii, which appear 
blue, as most do, the dots are always large and very close, while in E. s'parsus 
they are small and further apart. In one specimen, which I have not had 
time to figure, the dots are very small indeed. 
(In the recent gathering above referred to, E. Ralfsii is frequent, and I 
have found its colour, under the ^ to vary from purple to dark blue, bright 
