272 
age are the same as those now living in inhabitants of the ocean. Still 
when we remember that the fungus simply produces threads or fila¬ 
ments with the occasional addition of spores; that the bathymetrical 
conditions have probably remained nearly the same, and that the hosts 
alone have changed since early geological time; and further that the 
fungus causing potato rot had at least its representative in plants of 
Carboniferous age, it does not seem so strange to find long-lived forms 
under other conditions. If, however, the parasitic Adilya penetrans of 
modern seas is identical with the parasite of Silurian seas, the case is 
without a parallel in the organic world. 
In 1877 Prof. L. Lesquereux published a paper entitled U A species 
of fungus recently discovered in the shales of the Darlington coal bed 
(Lower Productive Coal Measures Allegheny River series) at Cannelton, 
in Beaver County, Pa. 1? * The name Rhizomorpha sigillaricv is given to 
the specimen, which was found beneath the bark of a species of /Sigil- 
laria. A figure of it was sent to Dr. Oasimer Roumeguere, of Toulouse, 
France, who concluded that it bore a great resemblance to living exam¬ 
ples of Rhizomorpha. The figure given by Lesquereux is reproduced 
below. (Fig. 1.) 
The striking resemblance which 
this figure had to certain insect 
burrows under the bark of trees 
was pointed out by the writer in 
1885 f and a further examination ' 
confirms this belief in its origin. 
The genus Rhizomorpha is now rec¬ 
ognized as simply the sterile myce¬ 
lium of various species of fungi. 
This fact does not of course mili¬ 
tate against the fossil being a fun- 
Pig. 1 .—llhizomorpha siaillarice . Lesqx. . , ., , 
gus, but it comparison be made be¬ 
tween it and the burrows of various living insects, the resemblance is 
most marked. Some of these are shown in the figures given on the fol¬ 
lowing page (figs. 2 and 3). 
The burrows, although more or less constant in form for each indi¬ 
vidual species, present great variations. With a sufficiently large 
series of examples it might be possible to find some presenting a greater 
resemblance to the fossil, but the general aspect of the modern insect 
mines is sufficient to induce the belief that the supposed fossil is not a 
fungus but an insect burrow. This tact is rendered the more probable 
when it is remembered that remains of insects are found in the same 
beds as those containing the fossil Rhizomorpha. 
* Proc. Am. Phil. Soc., Pliila., Vol. xvn, 1887, pp. 173-175. 
+ Remarks on a supposed fossil fungus from the Coal Measures, Jour. Cju. Soc, Nat. 
Hist., Vol. via, 1885, pp. 157-159. 
