Diatomaceous Sand of Glenshira. 
43 
they atre distinct. Indeed N. palpehralis is a very small form, 
while N. angulosa is generally large and conspicuous. But 
the angular space in the middle in both varieties of N. angu- 
losa, is a good and permanent mark of distinction. (266.) 
9. Navicula Macula, n. sp. This is a very remarkable form, 
which is not rare in the lighter densities of the deposit ; but I 
have never seen it elsewhere as yet. 
Form elliptic in the middle, short, contracted, and again 
slightly expanding to very obtuse, almost truncate apices. In 
shape it is not unlike the larger specimens of Cocconeis flexella 
{Thwaitesii, Sm.). Length, 0-0015" to 0-002". Median line 
straight, abruptly terminating at two points some way on each 
side of the centre. There is no central nodule, but only a 
large blank space, the length of which lies across the middle 
of the valve, and which looks like a stain. Beyond this, 
towards each end, the valve is very finely striated. Striae about 
70 in 0*001", transverse and parallel. 
The peculiar blank central space, which is not at all like an 
expanded nodule, differs from anything I have seen in any 
other form. I have examined not less than 100 specimens, 
and in none of them could I see any appearance of a central 
nodule, nor could I trace the median line farther than the 
margin of the blank, as we can do in so many forms where the 
nodule is expanded. 
Fig. 9 is a very accurate representation of this form, which 
is remarkably uniform in its characters. (267.) 
10. Navicula Solaris, n. sp. This is a very pretty and well- 
marked form, frequent in the middle densities of the deposit. 
It is represented in fig. 10. 
Form rhombic, long and narrow, with obtuse extremities. 
Lehgth from 0-0015" to 0-0045". The striation is fine, but 
very distinct, even conspicuous, very much inclined towards 
^, the ends, and in the centre, where there is a small circular 
blank spot, so highly radiate as to present the appearance of 
a sun with rays. Striae 36 in '001". The valve is usually of 
a brown colour, more or less deep, even in balsam. There is 
some resemblance between the shorter individuals and P. ra- 
diosa ; but ]V. Solaris, besides having finer striae, and those 
more inclined, is usually much longer. As both forms occur 
in the deposit, they are easily seen to differ very materially in 
aspect. I have not yet observed it elsewhere. (268.) 
11. Navicula Pandura, Breb. ? In the course of last year 
a very beautiful form was described and figured under this 
name by de Brebisson as occurring in sea water at Falaise. I 
have here given under this name, as a British form, that which 
is represented in fig. 11, although it does not appear to be in 
all points identical with that of de Brebisson. But the (jlen- 
