West, on Diatomacece. 
149 
difficult. Ehrenberg^s species occurs in the Bermuda deposit, 
whicli contains only strongly siliceous forms, has no pseudo- 
nodule," and is, I believe, perfectly plane on the surface. 
Mr. Brightwell first announced the true nature of the so- 
called " pseudo-nodule," and the occurrence of frustules 
attached in filaments in this condition. I have pleasure in 
being able to show an original drawing by Lieut.- Col. 
Baddeley, of Clifi" Cottage, Gorlestone, who has had ex- 
tended opportunities for investigating this and the following 
species, which he has taken great pains to clear up. 
T. Brightwellii, T. W. (Fig. 6.) 
Central spine of great length, with a fringe of obtuse spines 
round the margins of the valve. 
This species, well characterized by the extraordinary length 
of the central spine, which is throughout of equal thickness, 
and the remarkable fringe around the margins of the valve, 
cannot have a more appropriate name than that of him who 
might almost be called the author of the genus. In addition to 
the Gorlestone habitat, it has been found at Teignmouth. From 
the delicacy of the cingulum, and the great distance to which 
the frustules are pushed by the development of the spines, it is 
probable that they are generally solitary and never form 
a lengthened filament. Mr. Brightwell, fig. 2, PI. VIII, 
(^Micr. Journ.,^ vol. vi), represents T. intricatum, T. W., 
two frustules attached ; his fig. 1, a side view of T. Bright- 
wellii, with the inflated lateral margins (the coronet of spines 
has been overlooked by the draughtsman) ; fig. 4 of the same 
plate represents the front view of two frustules of T. Bright- 
wellii, after recent subdivision, attached by the connecting 
membrane ; fig. 3, the same shortly before the occurrence of 
subdivision ; fig. 5, a four-sided frustule, the upper valve pre- 
sents a nearly complete side view, the central body within 
the connecting membrane shows the two new half- frustules 
forming in the early stage of subdivision, now detached from 
their proper position, and free within the connecting mem- 
brane. 
T. variabile, Br. Front view. (Fig. 7) 
The front view of this species only differs from that of its 
nearest ally, T. alternans, in the possession of a greater num- 
ber of strong siliceous lines. 
2. ASTERTONELLA, HaSS. 
A. formosa. Hass. (Fig. 8.) 
Side view linear, inflated towards the base, capitate at both 
ends, the lower (attached) extremity the larger ; numerous 
frustules occasionally adhere, and then form a flat -spiral, like 
Meridian circulare. 
