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 occurs in great abundance attached to the ex- 

 terior of 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 ORTONIA (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.), 0. minor (Nich.), and 

 0. carbonaria (Young), the first two from the Lower Silurian, and the last from the Carbo- 

 niferous Kocks. 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 marked 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. 55i.)on thelatero- 

 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 1 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 

 mouth of the tube. Hence in these genera the annulations 

 of the tube are produced by the lower edges of the segments. 



Ortonia intermedia (Nich.) a. One of the . r. J e . 



tubes enlarged ; 6. another example, in In Ortonia intermedia on the other hand, in some ex- 



which the simulations are greatly extended i , f f i t^pie porvmosed of a series of short 



laterally, enlarged. From the Hamilton a ;" anv rare > IJ "" . M1 



Formation. imbricating conical segments, the larger ends of which are 



directed towards the aperture ; and it is, therefore, the upper edges of the segments which 

 form the annulations. 



The species to which 0. 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. 



0. 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. 



