Diatomaceous Sand of Glenshira. 
69 
Form a broadish oval. Length, 0-0005'' to 0-001". Me- 
dian line strong ; no nodule. The transverse lines are strong 
entire costse, which I formerly described as double lines. 
This is only apparent, something on the form of the costae 
causing their margins to come out strongly. The space be- 
tween each pair of costse is striated at right angles to the 
costae, a character only seen on close inspection, and which I 
have observed since my former paper. This is a perfectly 
characterised species, which I have found pretty frequent in 
the recent gathering above mentioned. (219.)"^ 
28. Cocconeis (?) lamprosticta, n. sp. This form is some- 
what scarce in the deposit, and I have considerable doubts as 
to its belonging to this genus. For the present, however, I 
place it there, as I have not yet been able to see any other 
view than the one figured, of which I have found a con- 
siderable number. 
Form between elliptic and obtuse rhombic, inclining rather 
more to rhombic. The central nodule is not strongly marked, 
but the median lines terminate in two small expansions, be- 
tween which is a considerable space. Length from 0-0028" to 
0'0033". Striae about 12 in 0-001", very conspicuous, formed 
of dots, somewhat like those in C. distans, and as widely 
apart. There is a narrow blank space on each side of the 
median line. The dots have the same shining aspect as in C. 
distans, hut the form is much thicker and more strongly marked. 
The resemblance of this form, which is represented in fig. 
28, to C. distans in several characters, led me to refer it to 
the same genus. But in some specimens, apparently of the 
same form, the median line is a mere blank or raphe, and the 
dots are rather square than round. These specimens, as Dr. 
Greville pointed out to me, seem rather allied to Biddulphia 
or Zygoceros, genera which possibly ought to be united, and 
which, at all events, are very imperfectly known. , If the 
present form, fig. 28, belong to Biddulphia, it ought to exhibit 
the characteristic and peculiar front view of that genus ; but 
for this I have sought in vain. It is possible that there may 
be two forms; one a Cocconeis, or possibly a Navicula, the 
other a Biddulphia or Zygoceros. I figure the most frequent, 
and leave the question to continued observation. (282.) 
Before quitting this genus, I may mention, that in this de- 
posit both Cocconeis Scutellum and C. Placentula are among 
the most abundant forms, and that both of them exhibit a re- 
markable extent of variation. According to many, the form 
I figured in my first paper as C. speciosa is a form of C. Scu- 
* So numbered in Part I. 
