68 
Dr. Gregory, on the Post -tertiary 
aspect_,and appears sparsely dotted. In C.Scutellum, of the same 
size, and of the coarsest variety, there are twice or thrice as 
many lines, and in each line three or four times as many dots 
as in C. distans. Moreover in C. Scutellum, which has the 
striated aspect in all its forms, the dots are of very unequal 
size, being smaller in the middle, and increasing in size 
towards the margin. Again in C. Scutellum, the form of this 
valve is very often, indeed generally, more or less angular, 
both in the middle and at the apices. In C. distans, the dots 
are quite round, and have a peculiar lustre, so that in a certain 
focus they appear white and translucent. I have seen this 
form in recent marine gatherings, but it is scarce. (218.)^ 
(Since the above was written I have observed another well- 
marked character in this species. The granules or dots are 
placed on faint white transverse bars, which, in some positions, 
or in some lights, are easily seen. I have also lately found 
C. distans, in considerable abundance, in a recent marine 
gathering, of which I hope to lay an account before the 
Society next season. In this gathering I have found two re- 
markable forms, which may perhaps both be varieties of C. 
distans, but one of which, though allied to it, is probably a 
distinct species. One of these has the faint white bars above 
described, and, on the whole, my observations tend to show 
that C distans is not related to C. Scutellum. 
I may here mention that C. costata, to be presently de- 
scribed, also occurs in the new recent gathering, and that this 
form also is entirely distinct from C. Scutellum, although Pro- 
fessor Smith, in his second volume, has conjectured it to be a 
form of that species.) 
26. Cocconeis radiata, n. sp. This very beautiful form is- 
rare in the deposit, compared with most of the others. It is 
represented in fig. 26. 
Form oval. Length about 0'00075". It has strong, distant 
rays, proceeding from a small, oval central spot, and, so far as 
I know, it is the only oval form which is radiated. The rays 
appear to increase in width as they approach the margin, and 
are crossed by a series of concentric elliptical lines, from the 
margin to the centre, giving to the valve a singularly rich 
appearance. Rays about 18; concentric ellipses about 7 or 8. 
This form has occurred as yet only in this sand. Fig. 26"^ re- 
presents an abnormal form of it. (282.) 
27. Cocconeis costata, n. sp. This pretty species was described 
in my former paper, but the specimen there figured was an 
inferior one. I give a better in fig. 27. It is not rare in the 
lighter densities. 
* So numbered in Part I, 
