238 Miscellaneous. 
stained with dark matter. The meshes are nearly black, but in a 
bright light show a fibrous texture and metallic lustre, due to 
pyrite. 
Viewed as opaque objects under the microscope, the reticulating 
bands are seen to be fascicles of slender cylindrical rods or spicules 
varying much in diameter, some of the largest being in the narrow 
transverse bands. The spicules may in a few cases be seen to be 
tapering very gently to a point, but usually seem quite cylindrical 
and smooth. In their present state they appear as solid shining 
rods of pyrite. The largest spicules are about =}, of an inch in 
diameter, the smaller scarcely one fourth of that size. The-spicules 
of the transverse bands cross those of the longitudinal ones without 
any organic connexion. Among the long spicules of the bands can 
be seen multitudes of very minute and apparently short spicules 
confusedly disposed ; and these abound also in the dark-coloured 
areoles. 
On the whole the structures are not identical with those of any 
plant known to me, and rather resemble those of siliceous sponges 
of the genus Huplectella. 
The most puzzling fact in connexion with this view is the mineral 
condition of the spicules, now wholly replaced by pyrite. Carbo- 
naceous structures are often replaced in this way; and so are also 
calcareous shells, especially when they contain much corneous 
matter; but such changes are not usual with siliceous organisms. 
If the spicules were originally siliceous, either they must have had 
large internal cavities which have been filled with pyrite, or the 
original material must have been wholly dissolved out and its place 
occupied with pyrite. It is to be observed, however, that in fossil 
sponges the siliceous matter has not unfrequently been dissolved 
out, and its space left vacant or filled with other matters. I have 
specimens of Atylospongia from the Niagara formation which have 
thus been replaced by matter of a ferruginous colour; and in a 
bundle of fibres, probably of a sponge allied to Hyalonema, from the 
Upper Llandeilo of Scotland, I find the substance of the spicules 
entirely gone, and the spaces formerly occupied by them empty. It 
should be added that joints of crinoid stems and fronds of Fenestella 
occurring in the same specimen with the Uphantenia are apparently 
in their natural calcareous state. 
Though I have hitherto regarded this curious organism as a 
fucoid, I confess that the study of the specimen above referred to 
inclines me to regard it as more probably a sponge. 
I owe the opportunity of examining this very interesting speci- 
men to the kindness of Professor Whitfield Amer. Journ. Sci., 
Aug. 1881, p. 132. 
Mortality of Fish in the Gulf of Meaico. 
From notices appearing in the ‘ Proceedings of the United States’ 
National Museum’ it appears that for the last two years there has 
