506 PROFESSOR GREGORY ON 
(Since this paper was read, I have ascertained that the peculiar plates above 
mentioned in Apr. pusilla, and in Apr. plicata, occur also in this species. I had 
overlooked them, from their being very narrow. ‘They rise from the inner margin 
of the valves, as seen on the F.V., from two points a short distance from the ex- 
tremities. Their convex margin extends in the middle just beyond the constric- 
tion. They are so narrow as to be readily overlooked, but are quite distinct, 
and appear to be thicker at the outer or convex margin than at the inner or plane 
one. There is even some appearance of a second plate in each valve, rising from 
the same line, as that just mentioned, but apparently extending in a plane at 
right angles to the surface of the valve, so that, in the F.V., it is seen foreshortened. 
and appears as a dark line. But I am not yet satisfied about this second plate. 
The plates first named constitute a very peculiar feature, both in this species, 
and in the two previously described. We shall see the same structure still more 
developed in another species, a very remarkable one, namely, Apr. maxima.) 
The form represented in fig. 59 c, I am satisfied belongs to this species; but I 
do not quite understand its relations. It is of an elegant rhombic-lanceolate 
form, with two curve-lines on each side, which at the middle bend inwards, to 
join a strong stauros, interrupting the median line, and at the ends coalesce with 
the margin. The whole valve is marked with fine parallel striee, except the 
stauros. This form, as will be seen, differs considerably from the usual 8.V., (fig. 
59 6), which latter often occurs with the longitudinal lines in it much more curved 
than in the example figured. Can the lateral lines in fig. 59 ¢ be the outer mar- 
gins of the two plates, above described, or perhaps of those suspected to lie in a 
different plane ? 
This species first occurred to me in the Glenshira Sand, and I figured the 8.V. 
as Apr. vitrea, 8? in my first plate of that deposit (Mic. Jour., vol. iii., pl. iv., 
fig. 14, the larger of the two figures, which shows the curved lines above alluded 
to, with a third line to the side); and the F.V. in my third plate (Zrans. Mice. 
Soc., vol. v., pl. i., fig. 39). But the former had not the strize, and the latter was 
from a very inferior specimen, and, besides, did not show the peculiar plates. 
I have therefore figured both views here from good specimens, which are frequent 
in Mr Mires’s Corallina gathering from Corriegills, near Lamlash Bay. It is at 
once distinguished from Apr. didyma by its much more elegant form, and by 
being twice as long. The 8.V., also, is quite different. Iam informed by Dr 
Grevitte that he finds this form abundantly, even predominating, in a dredging 
or gathering from nearly the same locality, which he made early last summer. 
60. Amphiprora obtusa, n. sp. Pl. XIL, fig. 60. Form of F.V. linear, broad, 
with rounded ends, slightly incurved in the middle. The termination of the 
middle space projects a little beyond the general curve of the apices. The inner 
margin of the striated part of the valve is gently and gracefully curved, forming 
two concave lines towards the middle, which meet in a point of the inner margin 
