169 
with descriptions of new genera and species. 
Orthoseira Dickieii was kindly comnumicated to me by Dr. 
Dickie, who discovered this beautiful species in December last 
near Aberdeen in a moist dripping dark cave close by the sea, 
and covering the Mosses, Hepaticse, &c. as a fine blackish green 
sand, collecting also in the shelvings of the rock. 
Oyclotella't Kiitzingiana, n. sp. PI. XL fig. D 1-5 (?|). Cel- 
lulis latere primario sigmoideo-flexuoso, lateribus secundariis 
radiatim striatis. 
The frustules of this species, fig. D 1, 2, are short, and exhibit 
an apparent sigmoid curvature, which is due to each of their stri- 
ated disciform ends having a prominence on one side of its centre 
and a depression on the other, and the opposite end of the frus- 
tule having a depression and prominence corresponding to these. 
The sporangia, fig. D 8, 4, are developed much'in the same way 
as in Meloseira. This species is evidently closely allied to Cy- 
clotella ? ininutula, Kiitz. Bacill. tab. 2. fig. 3, but differs in the 
fewer number of curvatures apparent in the frustule. The spo- 
rangial frustules, fig. D 5, are very similar to Cyclotella ? Rotula, 
Kiitz. Bacill. tab. 2. fig. 4. A species of Cyclotella collected by 
Geo. Dansey, Esq. near Devonport, and which I suspect maybe 
the C. operculata of Kiitzing, differs from the present species in 
the radiating strise being only slightly marked, and in the curved 
appearance of the frustule being scarcely evident. 
Occurs in brackish ditches amongst the leaves of MijriopliyU 
lum, &c. Wareham, Bev. W. Smith ; Shirehampton near Bristol, 
G.H.K.T. 
Before taking leave for the present of the Meloseirece, I cannot 
avoid referring to the analogy they offer to the genus Tiresias, 
Bory [(Edogoniujn, Link, Vesiculifera, Hassall), and its allies. 
The Meloseirece seem to bear the same relation to these that the 
other Diatomacece do to the Conjugates. The annulated struc- 
ture of the sporangium of Orthoseira also recalls to mind and 
explains the character of the rings which are met with at the end 
of the fructifying cell in Tiresias. 
Schizonema eocimium, n. sp. PI. XII. fig. F I (A), 2, 3, 4 (-^). 
Cselomatibus simplicibus ant parce ramosis, rugulosis : navi- 
culis sigmoideis Isevibus. 
The sigmoid frustules of this beautiful freshwater species at 
once distinguish it from any other described Schizonema. The 
delicate gelatinous sheaths are simple or very sparingly branched 
and minutely rugulosc, especially near their base; they contain 
from one to four rows of the large, smooth, sigmoid frustules. 
