122 
I cannot identify this pretty little form with any previously recorded. It presents the pe- 
culiarity that individuals in other respects precisely similar (Fig. 54 b,c) are sometimes dextral 
and at other times sinistral, the latter being the commonest upon the whole. The terminal por- 
tion of the tube is sometimes non-adherent and elevated above the surface, and the species is 
very readily recognized by its minute size, and its surface-ornamentation. It appears to be 
quite distinct from S. angulatus (Hall), which, so far as I am aware, is the only species yet 
recorded from the Hamilton Formation. It occursin great abundance attached to the ex- 
terior at species of Heliophyllum and Cystiphyllum, and also occasionally attached to Bra- 
chiopods. 
Locality and Formation.—Hamilton Formation, Bartlett’s Mills, near Arkona, Town- 
ship of Bosanquet. 
Genus OrnTonta (Nicholson). 
Animal solitary, inhabiting a calcareous tube, which is attached along the whole of one 
side to some foreign body. Tube slightly flexuous, conical, in section cylindrical, or some- 
what flattened laterally and sub-triangular ; surface marked with encircling ridges or annula- 
tions which may be confined to the lateral surfaces of the tube, or which pass completely 
round it. 
The only recorded species of the genus are Ortonia conica (Nich.), O. minor (Nich.), and 
O. carbonaria (Young), the first two from the Lower Silurian, and the last from the Carbo- 
niferous Rocks. It is, therefore, interesting to find a species of the genus in the Devonian 
Rocks, thus occupying an intermediate position in point of time as regards the species 
already known. 
152. ORTONIA INTERMEDIA (Nicholson). 
Tube conical, straight or flexuous, attached by the whole of one surface to some foreign 
body. Length, when fully grown, from a line and a half to two lines ; diameter of the aper- 
ture somewhat less than a line. Surface marke with strong encircling, sometimes lamellose 
annulations or ridges, of which there are about eight or ten in the space of one line near the 
mouth, but more than twice the number in the same space towards the closed end of the tube. 
Sometimes, the annulations are extended into wing-like prolongations (Fig. 55.)on the latero- 
inferior aspects of the fossil, and the tube is attached by means of these to the surface to 
which it is adherent ; and in all cases they are more pronounced on the sides than on the aspect 
opposite to the surface of attachment. 
= Ortonia intermedia is distinguished from .the other 
species of the genus by good and easily recognized characters. 
==) Some examples, indeed, exhibit a structure which has not 
otherwise been clearly detected in the genus—namely, 
that the tube is made up of a succcession of imbricating 
conical segments, the upper edges of which produce the en- 
circling ridges or annulations. A somewhat similar struc- 
ture is seen in Cornulites and Conchicolites ; but in these 
genera, the segments of the tube are inversely conical, or, in 
other words, have their smaller ends directed towards the 
rig Ge. mouth of the tube. Hence in these genera the annulations 
Opiate Gabarmnedén (Mich:) |9,, O1eror the of the tube are produced by the lower edges of the segments. 
tubes enlarged ; b. another example, in In Ortonia intermedia on the other hand, in some ex- 
Iaterally, sulared, » Fron the Hamilton amples at any rate, the tube is composed of a series of short 
Formation. imbricating conical segments, the larger ends of which are 
directed towards the aperture; and it is, therefore, the wpper edges of the segments which 
form the annulations. 
The species to which O. intermedia is most closely allied is 0. minor (Nich.), but the 
tube is not so strongly bent towards its closed extremity ; it is upon the whole a decidedly 
larger and more robust form ; and the annulations are considerably more remote and stronger. 
O. intermedia occurs attached to the exterior of various species of Cystiphyllum and He- 
liophyllum ; and it is always strictly solitary, though three or four individuals often occur 
Within a space of a few lines. 
