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PROCEEDINGS OF SOCIETIES. 
its organic elements to their nutriment. They vary in their relation to 
the bedding, sometimes passing through it almost vertically. They do 
not present any traces of a tube, and may, therefore, be looked on as the 
tracks of worms similar in their habits to those which are at present to 
be found sometimes in myriads in ooze in which much organic matter 
is present. They occur in the beds in immediate connexion with the 
Oldhamia at Bray and Grey stones, chiefly in the red beds, in. immense 
numbers ; more sparingly in the green beds, and also among Oldhamia, 
but evidently having no special connexion with it. They must have 
been very active when alive, or else extremely numerous, as the beds 
are in many places actually knit together by them. 
Tubuli of a similar character are also found in Puck’s Bocks and 
other localities at Howth, where, in the weathered rocks, they present 
an appearance similar to the so-called “ FucoidsA These latter may be, 
and probably are, formed by a distinct species from those at Bray, at least 
the mounds of Arenicola piscatorius , when disturbed, give an appearance 
very similar to them. 
2nd. A series of thread-like tubuli, vertical to the bedding, having 
slightly trumpet-shaped openings, and arranged in pairs apparently iden¬ 
tical with tubuli described as Arenicola didyma , in the rocks of the Long- 
mynd, by Salter. These two forms have been figured by me in the 
volume of the “Natural History Beview” for 1857, and also in the 
“ Transactions” of this Society for the same year. They must have been 
formed in a still estuary. (Vide Plate I., Pig. 3.) 
3rd. But by far the most remarkable form is that now to be described, 
and which, as far as I can make out, has not been hitherto known, viz., 
the tubes of 
Histioderma Hibernicum ( mihi ) (Wov, Sep/ua) Plate VI., Pigs. 1 and 2. 
Worm inhabiting a tube and forming a mound. Tubes membranous, 
from 0*75 inch to 3 inches long, and 0-5 inch in diameter; vertical to 
bedding ; superior extremity of tube trumpet-shaped; inferior turned up, 
and forming a chamber closed at the extremity. 
Head of worm tentacled and branchiated; tentacle casts dichotomous, 
1*0 inch, or upwards in length. 
These are found in several localities at Bray and Greystones in a 
close greenish grit; they occur in profusion, and appear to have been in 
some of their habits, as to burrowing, not dissimilar from the common 
lug-worm (Arenicola) of our present seas, but the tentacles (?) are ar¬ 
ranged similarly to those organs in Sabella or Terebella, to which they 
are probably allied. 
They formed numerous mounds some inches in height, somewhat 
pyramidal in form, in centre of which was the aperture of the hole. 
The beds in which they occur overlie the Oldhamia beds, and are 
many of them in a fine state of preservation, the ripple-mark, and other 
characters of the ancient shore in which they formed a prominent feature, 
being well seen. They were evidently Cephalo-branchiate; the wrinkles 
of their membranous tubes are easity seen in many specimens (Plate VI., 
Pig. 1.). 
