524 PROFESSOR GREGORY ON 
is transversely striated; but the strize cannot be traced throughout without alter- 
ing the focus. Strize about 38 in 0-001". 
This remarkable form was first described by Dre Bresisson as occurring near 
Cherbourg. No form is better adapted to show the structure of a complex Am- 
phora, on account of its transparency, and the breadth of the convergent bars. 
I have found it in Lamlash Bay, where it is not very frequent; and also sparingly 
in Loch Fine. No detached segments have yet occurred. 
93. Amphora acuta, n. sp, Pl. XIV., figs. 93 and 936. Form of detached 
segment arcuate, dorsal margin convex; in some examples with a slight inflec- 
tion just before the extremities; ventral margin straight, or slightly concave, 
ends acute. The inner lines are very near the ventral margin, and almost ex- 
actly parallel to it, but sometimes a little incurved, except in the middle, 
where the nodule meets them. Nodule elongated into a strong transverse 
bar. Length of segment 0°0035" to 0:0055"; breadth of it 0:00075". The seg- 
ments are marked by transverse strize, about 36 in 0-001’, which are distinctly 
moniliform. 
I have not yet seen the entire frustule ; but it is no doubt complex, for I found 
a good many half-frustules, as it were, formed of segments lying one over the 
other, to the extent of five or six. Sometimes no cross bar is seen, probably be- 
cause the cross bar is only found on the lateral segments, which may have be- 
come detached, and left the middle ones by themselves. One figure shows a group 
or pack of segments. 
This species occurs in Lamlash Bay, but is more frequent in Loch Fine. It 
is probable that the entire frustule will somewhat resemble A. nobilis in form, 
but not in its hyaline aspect. On comparing the segments of A. acuta with those 
of A. nobilis, as seen in the entire frustule, the curve lines in the latter are seen 
to be very deeply curved, and to be much farther from the inner margin of the 
segment, whereas the inner lines in the segments of A. acuta are straight, or very 
nearly so, and close to the ventral margin. In A. acuta, the strie, though not 
coarse, are strongly moniliform, while the strize of A. nobilis are much finer. Yet 
it is probable that these two species are related. 
(I have very recently observed two specimens, apparently of A. acuta, in which 
two segments are placed opposite, and close to each other. I suppose this view 
to represent the flat side of the frustule, or the half frustule, like a cut orange, as 
in the figure of A. Grevilliana, fig. 89. But in these specimens of A. acuta, the 
two lateral segments are in apposition.) 
94. Amphora crassa, Greg. Pl. XIV., figs. 94, 946, 94¢,94d. Form of frus- 
tule rectangular, broad, with rounded ends. Length from 0:0025" to 0-004’; 
breadth from 0-0008’ to 0:0013”. Lateral segments linear, from 0:0005" to 0:00075" 
in breadth, straight, or very slightly incurved on the dorsal margin, which, at 
the apices, bends inwards, forming short, rounded beaks. Sometimes, as in one 
