Greville^ on New Diatoms. 
13 
cancellated cellulate arrangement, witli the liglit coming 
through the interstices so clearly as to establish its character 
beyond dispute. The beautiful concentric cellulation is also 
totally wanting in A. Or eg anus. On the other hand, there 
is a great resemblance in the numerous processes. In both 
species they are linear when viewed laterally ; but in our new 
species they are not so apparently " emarginate ^' as they 
have been defined to be in A. Oregamis. When very 
minutely examined, however, the processes in both are found 
to be rounded at the apex. The furrows in our present 
species are extremely narrow, having much the appearance 
of transparent ribs, dilating suddenly into small, blank spaces 
at the processes. My friend, Mr. George Norman, informs 
me that on searching his slides marked for A. Oreganus 
he has found a specimen of A. ortentalis in some pearl shell 
debris obtained from a dealer, the locality being unknown. 
BiDDULPHIA. 
BiddulpMa gigantea^ n. sp., Grev. — Side view more or less 
broadly elliptical, subacute, inflated ; horns long, cylindrical, 
capitate ; cellules large, radiating. Longest diameter about 
•0080" (fig. 9). 
Hab. Barbadoes deposit, Cambridge estate ; C. Johnson, 
Esq., E. K. G. 
Of this magnificent species I have seen several tolerably 
entire valves, besides fragmentary ones. Perfect horns, 
however, are very rare, as, being long and slender, they are 
readily broken off^. The large subquadrate cellulation, 
inflated centre occupying nearly the whole surface, and flat 
margin, conspicuously distinguish it. The ends are carried 
out considerably beyond the base of the horns, like the ears 
of the Scottish shallow drinking-cup called a quaich, which 
the valve not a little resembles, especially the broad form 
represented in the figure. Generally, the outline is much 
narrower, more or less oblong; but the leading characters 
remain essentially the same. 
Triceratium. 
Triceratium concinnmn, n. sp., Grev. — Valves with straight 
sides, rounded angles, and very remotely scattered puncta, 
the centre an obscurely defined triangular space ; margin 
with a row of puncta, and the extreme angles with a dense 
