174 WALKER-ARNOTT, ON MARINE DIATOMS. 
Eunotia is strictly a fresh-water genus. I may here 
remark that recent observations on HE. diadema has convinced 
me that the character I proposed (‘ Micr. Journ.,’ vi, p. 202) 
for distinguishing Hunotia from Himantidium is not tenable : 
I must have been deceived by examining specimens at the 
period when the connecting zone was at its minimum, and 
inconspicuous. I am now quite satisfied that specimens may 
be found in perfect accordance with Smith’s figures. 
Epithemia is chiefly a fresh-water genus, although most of 
the species grow equally well im brackish water. It is also 
a truly parasitical one. Some species are no doubt found, 
not on filiform alge, but among the gelatine of Hemato- 
coccus and others of the Protococcee, to which they seem to 
attach themselves. H. musculus I have never seen, except: 
in salt marshes to which fresh water has access. . rupestris 
is said to be from fresh, and H. Westermanni from brackish, 
water; but this is lable to doubt, for EL. Westermanni of 
Smith can scarcely be distinguished from short forms of #. 
rupestris, and may have been carried down by streams, or be 
one of those that grow in both places. Thisis not H. Wester- 
manni of Kiitzing, a species which I have seen parasitic on the 
leaves of Zostera from the Baltic. E. musculus of Smith 
appears to be composed of two species, one which he has 
described in the text as having “striz 40 m ‘001,” and 
which I have in the same slide with H. Westermanni, Kutzg., 
and is the EH. musculus of Smith’s slides from the 8. of France 
(May, 1854); the other, or true EL. musculus, has distinct 
moniliform striz, and is that figured by Smith. The 
synonyms of the whole species are much confused in the 
‘Synopsis.’ H. constricta of Smith is certainly not that of De 
Brébisson, which is a much smaller species, destitute of the 
anterior keel to the valves (by which Smith’s is distinguished), 
and more allied to H. Westermanni of Smith. LE. alpestris of 
Smith’s ‘Synopsis,’ from Katefield, is not the species of that 
name distributed in slides by Smith, which latter wants the 
large foramina, and is that form of L. zebra called EL. librile by 
Ehrenberg. E. argus, EF. ocellata, and E. alpestris of the 
‘Synopsis’ are three varieties of H. ocellata (such is the 
oldest name), while E. longicornu is the sporangial state of 
the same. KH. Hyndmanni, Sm., and Eunotia Luna of 
Ehrenberg’s ‘ Mikr.,’ tab. xv a, fig. 58, are obviously one 
species; but Ehr. ‘ Mikr.” tab. xxxiii, xii, fig. 15, from 
Oregon, appears very different. The specific character given 
of HK. Luna by Kiitzing refers to the Oregon species only. 
In justice to Mr. T. Comber, of Liverpool, I ought to state 
that the preceding observations on this genus are the 
combined deductions arrived at by him and myself. I know 
