Dr. Greville on a new species of Spiridens. 325 
The freshwater Mussel [Mya margaritiferay L.) is abundant 
in both the Dee and Don. The specimens in whose intestines 
the following Diatomacece occurred, were from the former river 
eighteen miles inland. 
Meridtecs. 
Meridion circulare, Ag. 
FragilariecB. 
Fragilaria hyemalis, Lyngh. 
Diatoma flocculosiim, Ag. 
D. tenue, Ag. 
MeloseirecB. 
Meloscira distans, Kutz. 1 
Surirellece. 
Synedra capitata, Ehr. 
S. tenuis, Kiitz. 
CocconoidecB. 
Cocconeis Pediculus, Ehr. 
Intermixed with these were spiculse of Spongilla. Generally 
speaking the individuals of each species were of the minimum 
size, certainly far less than that usually attained. Of those 
brought within the sphere of the currents produced by the cilia, 
the smaller alone were swallowed. Of the species enumerated I 
have found the following on our mountains at heights varying 
from 2800 to 3800 feet : viz. Meridion circulare, Diatoma floccu- 
losum, D. tenue, Meloseira distans ?, Gomphonema pohliceforme, 
G. minutum, Navicula rhomboides ? and N. viridis. The Meloseira 
I have found to constitute a considerable proportion of the fine 
black mud found beneath patches of snow on Ben-na-Muich 
Dhu. 
XXXIV. — Notice of a new species of Spiridens. 
By R. K. Greville, LL.D. &c.* 
. [With a Plate.] 
The genus Spiridens, established by Nees von Esenbeck in the 
Ilth volume of the ^Nova Acta Acad. Cses. Leopold. Car. Na- 
turae Curiosorum,^ has hitherto contained the single species it 
was constituted to receive, viz. Spiridens Reinwardtii. This most 
noble of all mosses, as it is justly designated by SirW. J. Hooker, 
is a native of the Molucca Isles ; twelve inches or more in height, 
with a robust, Bartramia-like habit. It is figured in the Trans- 
actions above-mentioned ; but the British botanist will also find 
a figure and description in the first volume of Sir W. J. Hooker^s 
‘ Botanical Miscellany,^ published in 1830. 
* Read before the Botanical Society of Edinburgh, March 9, 1848. 
AchnanthecB. 
Achnanthes minutissima, Ehr. 
CymbellecB. 
Cymbella flexella, Kiitz. 
C. leptoceras, Kiitz. ? 
Cocconema cymbiforme, Ehr. 
Gomphonema geminatum, Ag. 
G. pohliaeforme, Kiitz. 
G. minutum, Ag. 
Namculece. 
Navicula rhomboides, Ehr.% 
N. cuspidata, Kiitz. 
N. viridis, Kiitz. 
