Greville^ on New Diatoms. 
91 
GlyphodiscuSj n. gen., Grev. 
Erustules somewhat four-sided, with the corners much 
rounded. Valve containing a large, four-cornered nucleus^ 
the'angles of which alternate with those of the margin ; and 
a circular prominent process within each marginal angle, from 
which costse radiate to the nucleus, while similar costse ra- 
diate from the angles of the nucleus to the sides of the disc. 
As nothing whatever resembling this most singular diatom 
has been recorded, I have been under the necessity of con- 
structing a genus expressly for its reception. With Auliscus, 
it has a decided affinity in the arrangement of the costse, and 
at first sight in the circular processes also. But after a close 
examination of a suite of specimens, I am satisfied that the 
processes are not flat and mastoid, as in Auliscus, but con- 
siderably prominent, although to what extent it is impossible 
to say, as no front view has been observed. The radiation of 
the costse is arrested almost immediately by the large nucleus 
which occupies the greater portion of the disc ; and this dense, 
opaque nucleus, with its four corners alternating with the 
rounded corners of the margin, has nothing in common with 
Auliscus. There is no other genus with which it can be 
brought in comparison, unless it be Amphitetras, on account 
of its somewhat cubical frustule ; but there is no affinity be- 
tween the apparent openings in the angles of that genus and 
the prominent processes in Glyphodiscus ; while in general 
structure there is not the most remote resemblance. 
Glyphodiscus stellatus, n. sp. Grev. (Fig. 5.) 
Hab. Monterey stone; F. Kitton, Esq., 1854; Professor 
Walker- Arnott ; G. Mansfield Browne, Esq. ; R. K. G. 
Disc minute, somewhat quadrate, but wdth the corner so 
much rounded as to bring the outline nearly to a circle. 
Within, the greater part of the area is occupied by a sort of 
dense, opaque nucleus, more decidedly quadrate than the disc 
itself, w^ith rounded or subtruncate angles, alternating with 
those of the exterior, and leaving but a narrow space between 
it and the outer margin. Within each of the outer corners 
is a large circular or somewhat oval process (as viewed verti- 
cally), at first sight resembling those of the genus Auliscus, 
but it is in reality so prominent as to be at least mammillate. 
From each of these processes costse radiate in a converging 
manner, exactly as in Auliscus ; while another set of similar 
costse radiate from the angles of the nucleus to the sides of 
the disc. In fact, if we were to imagine an Auliscus with 
