16 
Roper, on Biddulphia. 
power of 200 diam._, appear to be granules or dots ; but are 
resolvable, with an eighth objective, into minute hexagonal 
reticulations, which radiate from the centre to the cir- 
cumference of the valve. The spines are rather long, slightly- 
curved inwards, and arise about midway between the angular 
processes. The connecting membrane is closely covered 
with longitudinal rows of punctse. 
10. Biddulphia Indica, Ehrenberg (sp.) 
Valve lanceolate, slightly tumid in the centre, minutely 
punctate, with two long awl- shaped spines near the angular 
processes, which are long, narrow, somewhat capitate, and 
with the pseudo- apertures at right angles to the length of the 
valve. The surface of the valve covered with minute pointed 
spines ; connecting membrane marked with diagonal striae. 
(Plate II, figs. 20, 21, 22.) 
Marine? Natal, Shadbolt. 
Si/n. Denticella Indica? Ehr. Ber. Pro., 1845, p. 863. 
Tjuceratium contortum. Shadbolt, Micr. Jour., vol. ii, t. i, f. 7b. 
This small and peculiar form is rather hyaline in structure, 
and is not unfrequent in the Natal gathering described by 
Mr. Shadbolt in vol. ii of the Microscopical Journal,^ p. 15 ; 
but I am at a loss to imagine how he could describe and 
figure it as a front view of Triceratium contortum. I have 
carefully examined more than twenty slides of this gathering, 
and though there are several good single valves, I have only met 
with one perfect frustule, and this, as we should naturally 
expect, clearly shows the three angles and spines, of which 
there is no trace in the small form figured in tab. i, fig. 7 bj 
of the Journal. The marginal row of spines plainly visible 
on the side view of T. contortum, are also shown to arise 
from a siliceous fringe, somewhat similar to that figured by 
Mr. Brightwell in T. undulatum,^ and they are entirely 
absent in the frustules I am now describing, and their whole 
structure so entirely accords with that of the Denticella of 
Ehrenberg, now included in the present genus, that I have 
no doubt as to their proper generic position. 
With respect to its specific name there is the same doubt 
as with B. tumida. Ehrenberg describes a species obtained 
from the Indian seas, under the name of Denticella Indica, as 
"Testula Isevi (an subtilissime punctata) tubulis valde pro- 
ductis, sub-capitatis, aculeis longissimis, tubulos excedentibus, 
area inter tubulos aspera /^f biit I can find no figure among 
* 'Micros. Journ.,' vols, vi, tab. viii, figs. 4, 5. 
t 'Ber. Proc.,' 1845, p. 163. 
