Diatomaceous Sand of Glenshira, 
77 
4] . Campylodiscus simulans, n. sp. This is a fine form, and 
frequent in the coarser densities, though, like nearly all the 
forms described in this Paper, it has not yet occurred elsewhere. 
(I find it in the recent gathering above referred to, and 
I am informed by M. de Brebisson that it is the same 
as his A. Thuretii. But as I had found and named it, and 
even communicated it to M. de Brebisson long before his 
Paper appeared, I retain my own specific name. M. de Bre- 
bisson^s figure is not characteristic, or I should sooner have 
recognised the identity of the two forms.) 
Form frequently orbicular, and also frequently exhibiting 
the peculiar flattening at one side, and pointed projection 
opposite, with the saddle-like flexure of the valve so charac- 
teristic of the genus. But the orbicular individuals often do 
not seem to possess this last character. 
From two points, near to each other at the circumference, 
two lines proceed, diverging gradually to the middle, and con- 
verging again to two points opposite the first. These lines 
bound the median space which occupies, in the middle, about 
one fourth of the diameter. It is marked with coarse trans- 
verse striae, divided in the middle by a blank line or raphe. 
, From the margins of this space proceed, on each side, about 
twelve diverging lines, which, for rather more than a third of 
the distance to the circumference, are strong and black. 
Each line then splits into three, the two outer diverging a 
little, and near the margin meeting in a semicircular termina- 
tion, and thus forming, on each of the short black lines, as a 
stalk, a lotus flower ; the semicircular ends of these flowers 
meet all round, forming an ornamented inner margin. Beyond 
this lies a circular outer margin, and the short space between 
is transversely striated. At the points where the stalks of 
the lotus flowers divide, the third or middle line proceeds 
straight on from the stalk, and terminates abruptly just where 
the flower begins to expand into the head. Diameter from 
0-003 ' to 0-004". 
I have thus minutely described the markings of this form, 
which is well figured in fig. 41, because in my former Paper 
I figured another form, of a diff*erent genus, the markings of 
which are almost, if not quite identical with those of the form 
here described. That was figured as a large variety of Suri- 
rella fastuosa ; and although I had not then studied the struc- 
ture so minutely as I have since done, and the figure is not 
perhaps exactly as I would now make it, yet it will be seen 
that even that figure shows the resemblance. 
The only difference, except that of form, which I can per- 
ceive is, that in the Surirella, the median space is narrower. 
