Greville^ oh New Diatoms. 
31 
withstanding essential differences. Breadth of fnistule '0013''. 
Length -0050". 
H. longicornis, n. sp.^ Grev. — Not strictly rectangular, very 
minutely punctate,, puncta scattered ; valve with the angles 
produced into long, linear, more of less incurved horns tipped 
with two sharp teeth ; space between the horns with a single 
arch-like projection, (Fig. 13.) 
Hab. Barbadoes deposit, Cambridge estate j in slides com- 
municated by C. Johnson, Esq. 
The valve, in its front view (as figured), with its long and 
somewhat incurved horns suggests a resemblance to the shafts 
of a light carriage j occasionally, however, the horns, although 
inclined, are almost straight. They are very slender and have 
the appearance of being thickened upwards in consequence of 
a hyaline limbus or edging being more broadly developed 
towards the extremities where it terminates in the teeth. A 
beautiful row of minute dots passes down each horn. The 
breadth of the frustule is '0020''. Length °0035'^ 
H. alatus, n. sp., Grev. — Not rectangular, minutely punctate, 
puncta in irregular lines; valve with the angles produced 
into rather long linear, connivent, toothless horns, having a 
hyaline border; space between the horns with a small conical 
projection. (Fig. 14.) 
Hab. Barbadoes, Cambridge estate, but in a different 
sample of the deposit; in slides communicated by C. 
Johnson, Esq. 
This is a well-marked diatom and perfectly constant to its 
characters, differing only occasionally in its relative propor- 
tions. The whole surface is more obviously punctate than in 
any of the preceding non-rectangular species. The horns 
have a more carriage-shaft-like bend than even in the one last 
described ; but they have no terminal teeth, which is remark- 
able, because the hyaline limbus from which the teeth are 
apparently derived is here very strikingly developed. There 
is also a peculiarity in the hyaline margin on the inner side 
which I have not observed in other species. It is composed 
of two plates, one of which arises near the central projection 
and reaches nearly to the inward curve of the horn; the 
other commences at about the same point and is continued to 
the apex. The average dimensions may be set down as, 
breadth -0020'', length 0026''. Sometimes the breadth is 
greater, while the horns are at the same time shorter. 
hastatus, n. sp., Grev. — Valve very minutely and closely 
punctate, widely conical, the angles produced into stout, rough, 
diverging horns, terminated by long, hyaline, very acute. 
