152 
West, on Diatomaceae. 
mucli on a strong siliceous envelope being necessary to con- 
stitute a diatom. I believe, on the contrary, that the frus- 
tule may have very little silex_, but that the colour and dis- 
position of the endochrome furnish the only true grounds for 
classifying it/^ 
The filament is always 'enveloped in a thick covering of 
tenacious mucus, which renders its satisfactory examination 
difficult. That this is an integral portion of it I am led to 
believe by the fact, in the first place, of its being always pre- 
sent j and in the second, that when a frustule is found clear 
from it, as occasionally happens at the end of a filament, the 
endochrome is dead, and has more or less completely dis- 
appeared. 
C. horeale, Bail. 
The discovery by Mr. Atthey, on the Northumbrian coast, 
in the stomach of Modiola vulgaris, of this species, makes an 
interesting addition to our list of British Diatomacese, its 
recorded habitats having hitherto been on the American 
coast, and in the Indian Ocean, supposing C. Peruvianum to 
be the same thing, which is not yet clearly proved. The 
direction of the horns at right angles to the frustule in 
many of the British specimens (fig. 13) is a curious circum- 
stance. Along with it occurred Doryphora amphiceros and 
other commoner marine Diatomacese, with the doubtful 
Actiniscus Sirius, Ehr. (fig. 14), and some specimens of Poly - 
cystinece. 
5. Attheya^ nov. gen., T. W. 
Frustules quadrangular, compressed, annulate ; annuli in- 
definite ; valve elliptical lanceolate, with a median line ; a 
spinous process from each angle. 
A. decora, sp. T. W. (Fig. 15.) 
Annuli 12 to 28, 20 in -001 ; septa alternate. Width of 
frustule, -0009'' to -0015". Breadth of valve, '0003'', with 
a median line and distinct central punctum. 
Found by Mr. Atthey, plentifully on Cresswell Sands, in 
June, 1859, free from admixture; and again equally clean in 
May of the present year. Also with Podosira? compressa, and 
other diatoms of similar habitat, by the Bev. B. Taylor and 
Mr. Atthey, in the same place, and by the latter in Druridge 
Bay. The appearance of this pretty little species is precisely 
like Striatella umpunctata in miniature, the arrangement of 
the endochrome being also much the same in both ; from 
Striatella, however, it is separated by the presence of 
spinous processes at the angles, and the entire absence of 
stripes or attachment of any kind. Of the propriety of in- 
