52 
Greville, on New Diatoms. 
able to speak with certainty as to the precise situation of the 
spines ; but as all the specimens I have seen were alike, there 
would appear to be only three spines, and, as far as I can 
judge, two of them are exactly opposite the horns. From the 
singular angularity of the front view, it is not improbable 
that the top may be flat, as in B. Baileyi. Length of the 
valve, -0030^'; length of horns, '0018^ 
Biddulphia mtida, n. sp., Grev. — Small, punctate; valve in 
front view showing the horns to be produced considerably 
within the angles; horns elongated, erect, swollen and punc- 
tate at the base, somewhat capitate and curved outwards at 
the apex ; median space convex. (Fig. 11.) 
Hab. Barbadoes deposit, Cambridge estate ; in slides com- 
municated by C. Johnson, Esq.; extremely rare. 
A single but quite perfect frustule has only been disco- 
vered. The characters are very decided. The surface is 
conspicuously punctate, appearing almost rough. The con- 
necting zone smooth, as well as the horns above the swollen 
base. Breadth of frustule -0022''. 
PORPEIA. 
This getius, established by Professor Bailey, appears to be 
well founded. The incurved costal plates are probably never 
more than two in number, and in the new species about to 
be described assume a vei'y peculiar and marked character. 
Porpeia quadriceps, Bail. — (Figs. 18, 19.) Balfs, in ' Brit. 
Inf.,' 1861, p. 850, pi. vi, fig. 6. 
Hab. Barbadoes deposit, Cambridge estate ; in slides com- 
municated by C. Johnson, Esq.; rare. 
Frustules rectangular, minutely punctate; the angles of 
the valve produced into rounded capitate processes, the head 
of which is either supported on a short thick neck, or does 
not entirely rise above the level of the median space, as in 
Professor Bailey's drawing. This space, in small specimens, 
forms a simple arch, giving off the curved costse at, or close 
to, the angle, and in larger specimens an arch in the middle, 
while the space between the arch and the processes is nearly 
straight. In such cases the curved costse are given oflp at 
the commencement of the arch. 
Being under an impression that the diatom I have now 
figured may be the species proposed by my late friend Pro- 
fessor Bailey, I have refrained from separating it. At the 
same time it is necessary to remark that the figure engraved 
from his drawings in Pritchard's ^ History of Infusoria' does 
not correspond with any specimens in my cabinet. One 
