R. Etheridge, jun,—Carboniferous Tubicolar Annelida, 111 
Gyromices, Goppert, in Germar’s Verstein. Steinkohlen. Wettin u. Lobejiin, 1853, 
heft 8, p. 29 (r11.). 
Geinitz, Verstein. Steinkohlenform. in Sachsen, 1855, p. 3. 
Microconchus, Pictet, Traité de Paléontol. 1857, iv. app. p. 710. 
Gyromices, Geinitz, Dyas, 1862, heft 2, p. 133. 
Paleorbis, Van Beneden et Coemans, Bull, l’Acad. R. Bruxelles, 1867, 2me Ser. 
xxiii. p. 390. 
» Goldenberg, Fauna Sarzpontana Foss. 1877, heft 2, p. 4. 
Chars.—Tube dextral, or sinistral, attached by one side; simply 
spirally coiled, or the last volution extended into a free tortuous 
tube of greater or less length, but usually short; chambered or 
quite non-septate. Section ‘circular, or elliptical; margin of the 
aperture or mouth of the tube round or a little sigmoidal; attached 
side flattened or irregular, attachment taking place by the whole, or 
only a part of the surface : sometimes forms for itself a depression 
in the substance of the body to which it is fixed. Surface plain, or 
ornamented with microscopic concentric strie, or coarse annula- 
tions ; sometimes produced into spines along the periphery of the 
tube, or each annulation forms a projecting ‘Jamella, or the surface 
may be generally spinous, whilst occasionally fine spiral strie are 
present. Habit solitary, or found in large numbers together. 
Obs.—The foregoing diagnosis is drawn up to include the small 
tubicolar Annelides of our Carboniferous rocks (and it may be said 
Paleozoic rocks generally), usually referred to Spirorbis, and in 
some instances to Serpula. With the view of expressing their 
separation and probable distinctness from the living Spirorbis, and 
those found in much younger rocks, I have employed the name 
introduced by Murchison as a sectional term under Spirorbis. This 
will, in a measure, tend to mark and retain as a separate group a 
very interesting series of forms, differing in some minor particulars 
from the recent Spirorbis, but still clearly allied to them. 
The history of Microconchus will be found under that of the type 
species, M. pusi/lus, and it will only be necessary to notice now 
one or two points of general interest. In the first place, at least 
two species form for themselves depressions or hollows, correspond- 
ing to their outline, on the surface of those substances to which they 
are attached, whether animal or vegetable. With regard to the 
latter it might be contended that these hollows were caused by the 
pressure of the hard tube on the softer vegetable substance during 
entombment, and subsequent fossilization. In many cases, however, 
it can be unmistakably shown that the Microconchus has become 
inclosed within the substance of the plant, and in the case of shells, 
on which certain species occur plentifully, it appears to pass under 
the epidermis or outermost shell-layer. So marked is this, in the 
case of a species occurring in the uppermost Silurian beds at Lesma- 
hagow, that specimens of Modiolopsis, one of the characteristic fossils 
of the beds in question, and preserved as internal casts, are perfectly 
riddled with these little parasites, which have left their impressions 
deep in what would have been the shell-substance. Similar facts can 
be studied in connexion with the Anthracomye and other bivalves 
of the Wardie Shales, where Microconchus occurs in thousands, and 
under the same conditions, except that the shells in this case are 
not preserved as casts. 
