ON TRYBLIONELLA VICTORIZ AND DENTICULA SUBTILIS. 17 
Hooker, that the species of Diatomacee found on the Victoria could 
not have been brought from South America with that plant, for nothing 
but the seed had been imported originally or since,—no roots, no plants, 
no earth, no water. Besides, I find it associated with well-known* 
British forms, so that it must be held as truly indigenous to this 
country. 
I have not seen Dr. Grunnow's diagnosis of the species; but as my spe- 
eimens agree perfectly with his figure, I offer the following, to assist 
British botanists to determine this interesting and beautiful species :— 
TRYBLIONELLA Victorie, Grunnow, Verhandlungen der k.k. zool.- 
botanischen Gesellschaft, vol. xii. 1862, tab. xii. fig. 34 :—Valve 
linear, with obtuse ends, and generally with a very slight constriction in 
the middle, striated. Série stretching across the valve, those in the 
centre of the valve perfectly transverse, becoming very etd convex 
towards the ends, without a medial line; 18 in *001; canali 
lete. Length :0014, breadth 0007. 
This species is nearest to the marine 7. punctata, but it can be 
readily distinguished by its shape and the structure of the striæ. 7. 
punctata, in all its states, is without constriction in the middle, and 
always decreases from the broadest part of the valve towards the some- 
What acute apex, as represented in Smith's second figure, plate xxx. 
fig. 261; Grunnow's species, besides having the constricted valve, is 
rectangular, terminating in an obtuse apex. The strie of the first 
species are composed of a series of large dots, easily separated by a 
comparatively low power, while in the other species a very high power 
is required to resolve the small dots of the strize. The shape of 7. mar- 
ginata, and the faintness of the striae in the centre of the valve, pre- 
vent it from being confounded with the Kew species. 
Denticula subtilis, Grunnow, found in brackish water at Newhaven, . 
and described and figured in the same paper, is Smith's D. ocellata, 
Which he obtained, while the sheets of his second volume were passing 
through the press, from a gathering of Professor Balfour's collected 
near St. Abb's Head. It was not figured by him, but he gives a clear 
description, and adds that in the front view it closely resembles Zpithe- 
mia Argus, so that there can be little difficulty i in recognizing his spe- 
cies. Dr. Grunnow’s figure (1. c. tab. xii. f. 36) is the first published 
drawing of the species. 
VOL. I. c 
