84 
Dr. Gregory^ on the Post-tertiary 
surface is marked with very fine granulations_, among which 
may be observed faint rays, especially towards the margin; 
which is transversely striated, indicating a regular sym- 
metrical structure. I have not been able to determine the 
genus ; but as it seems to be cellular, I think it likely to be 
a Coscinodiscus. There are also two or three other discs 
which I am unable to name ; but I have not had time to 
obtain figures of them. (302.) 
51. Campy lodiscus. {?) This form, represented in fig. 50, 
has occurred to me several times. At first I took it for a 
Coscinodiscus, but on closer inspection it is found not to be 
truly orbicular, and rather to resemble a Campy lodiscus. It 
does not agree with any of the species in Smith's ' Synopsis 
but as it may be an immature form, I leave it for fiirther in- 
vestigation. 
Form quasi-orbicular, flattened a little at one side, and 
projecting a little at the opposite part. The markings consist 
of large sparse dots, arranged in a way which is partly radiate, 
partly in parallel lines, somewhat like Eupodiscus sparsus 
above described. There is some appearance among these 
lines of a broad rectangular cross, but not distinctly brought 
out. No central space, the dotted lines meeting in the 
centre. It is possible that it may, after all, be a Coscino- 
discus. (303.) 
(This form occurs, not unfrequently, in the recent gathering 
of which I have spoken above. It is sometimes, as in the 
figure, not exactly round, but it also occurs perfectly or- 
bicular. I hope to be able to study it more fully. It has 
some resemblance to Eupodiscus tenellus, Breb., but I cannot 
see in it the characteristic protuberance of Eupodiscus.) 
52. Amphiprora. {?) This little form is frequent in the 
deposit, and I have conjectured it to be an Amphiprora from 
its resemblance in form and general structure to that which I 
have above described as A. recta. It is represented in fig. 51. 
Form nearly rectangular, narrow; the ends rounded, obtuse. 
Frustule slightly constricted in the middle. The whole sur- 
face, except a narrow space in the middle, widening a little at 
the ends, is marked by transverse striae, which are conspi- 
cuous, radiate, and inclined, about 25 to 0*001''. There is, as 
in A. recta, an appearance of a central nodule visible on each 
valve, round which the striae seem to radiate. Length from 
0-0015" to 0 003'. 
At first sight this form, as well as A. recta, might be sup- 
posed to be the F. V. of a Navicula or Pinnularia. But 
among all the forms of these genera in the deposit, there is 
not one which agrees with this in its characters. Besides, 
