30 
Greville, on New Diatoms. 
Hah. Barbadoes deposit,, Cambridge estate ; in slides com- 
municated by C. Johnson, Esq. 
In none of the specimens which have come under my 
notice have I been able to see the minute teeth which we 
would naturally look for at the apices of the horns. The 
latter^ also, present a strange anomaly. In other members of 
the same group, or, at all events, very closely allied, the horns 
of opposite frustules are united by their ends; but in the 
present case it is impossible. In some specimens the apices 
even cross each other ; and in scarcely a single instance have 
I seen them otherwise than in contact. What can be the 
position of frustules in situ ? The size varies. The largest 
example I have observed has the length •0095^', the horns 
alone being -0050''. The breadth -0025''. 
H. lyriformis, n. sp., Grev. — Nearly smooth, not strictly rect- 
angular ; valve with the angles produced into long, narrow 
horns inclined more or less inwards, and tipped with two 
minute triangular teeth, and towards the base having ex- 
ternally a deep contraction ; between the horns a long, narrows 
central process. (Figs. 11,21.) 
Hah. Barbadoes deposit, Cambridge estate; in slides 
communicated by C. Johnson, Esq. 
A singular diatom^ but evidently belonging to the group 
under consideration. The body of the valve is small, serving 
merely for the stand, as it were, of the lyre-like horns. These 
are always inclined inwards, sometimes so much so as nearly 
to touch each other at the apex. The space between the horns 
is concave, the concavity being interrupted in the middle by a 
narrow, linear, erect process connected on each side with the 
horns by a hyaline limbus, which passes up their inner side. 
At the base the horns curve suddenly inwards so as to leave a 
deep notch between them and the bottom of the valve, giving to 
the whole organism the general appearance of a lyre. Breadth 
of frustule from •0014^' to -0026". Length '0025^' to '0030.'' 
H. angustuSy n. sp., Grev. — Narrow, very minutely punctate^ 
the puncta scattered ; valve with the angles produced into very 
long, linear, straight horns tipped with two acute triangular 
teeth and with a row of puncta down the margins ; space 
between the horns concave. (Fig. 12.) 
Hah. Barbadoes deposit, Cambridge estate ; in slides com- 
municated by C. Johnson, Esq. 
Although the horns of this species are straight in them- 
selves, there is a manifest tendency to an inward inclination ; 
so that it must range along with those in which the frustule 
(taken in connection with the horns) is not truly rectangular. 
With the following species there is considerable affinity, not- 
