200 Frof. H. A. Nicholson — New Devonian Fossils. 



surface to some foreign body. Length, when fully grown, from a 

 line and a half to two lines ; diameter of the aperture somewhat less 

 than half 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 

 this number in the same space towards the closed end of the tube. 

 Sometimes the annulations are extended into wing-like prolonga- 

 tions (Fig. 26, h) on the latero-inferior aspects of the fossil, and 

 the tube is attached by these to the surface to which it is adherent ; 

 and in all cases they are more pronounced on the sides than 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 structui-e which has not otherwise been clearly de- 

 tected in this genus — namely, that the tube is made up of a succes- 

 sion of imbricating conical segments, the upper edges of which 

 produce the encircling ridges or annulations. A somewhat similar 

 structure is seen in Cornulites and Conchicolites ; but in the*se genera 

 the segments of the tube are inversely conical, 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. In Ortonia intermedia, on the other 

 hand, in some examples at any rate, the tube is composed of a series 

 of short 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 nearly allied is 0. 

 minor, Nich. ; but the tube is not so strongly bent towards its closed 

 extremity ; it is upon the whole a 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 ffeliopJiyllum ; and it is always strictly solitary, 

 though three or four individuals often occur within a space of a 

 few lines. 



Locality and Formation. — Not uncommon in the Hamilton Forma- 

 tion, Bartlett's Mills, near Arkona, Township of Bosanquet. 



EXPLANATION OF PLATE IX. 



Fia. 16. — Botryllopora socialis, Nich. a. Portion of Heliophyllum Salli with a 

 small group of discs adherent to it, of the natural size. b. A single disc 

 enlarged, c. One of the radiating ridges enlarged to show the cells. From 

 the Hamilton Group. 



Fig. 17. — Oeriopora (?) Eamiltonensis, Nich. a. Portion of the stem, natural size, 

 showing the mode of branching, b. Fragment enlarged, showing the form of 

 the cells, and the tubular intercellular interspaces. From the Hamilton Group. 



Fig. 18. — Polypora pidchella, Nich. ; a. Fragment, natural size. b. Portion of the 

 reverse magnified, c. Fragment from which the non-poriferous layer has been 

 stripped off, showing the bases of the cells, enlarged, d. Cast of the inner 

 surface, enlarged, showing the cell-mouths. From the Corniferous Limestone. 



Fig. 19. — a. Fragment of the cast of Polypora HalUana, Prout, enlarged, b. Frag- 

 ment of the Cdi.si oi Polypora tenella, Nich., enlarged. Both from the Cornifer- 

 ous Limestone. 



Fig. 20. — Polypora tuberculaia, Nich. a. Fragment of the natural size. b. The 



