the septa, these structures being divisible into a double series of alternately long and short septa, of which the latter are quite rudimentary and marginal, while the former vary greatly in their development. Sometimes they fall short of the centre by a considerable interval-as is also usually the case in C. alveolata -but in other tubes they nearly or quite reach the axis of the visceral chamber. Moreover, the phenomena which the septa exhibit are precisely such as every student of the Rugose corals is familiar with. The longer septa, namely, are not of uniform length, but exhibit clear differences in their development, almost amounting to that produced by the existence of regular "cycles." Some of them quite reach the centre, others fall a little short of it; and there is even a tendency to the production of a single predominant septum, or of two such, towards the sides of which the remaining septa bend. Lastly, it is quite common for the longer septa to be more or less united with one another by their inner ends in a series of fascicles, though at other times each may be quite free.

Vertical sections of the corallum show no features of special structural importance (Pl. X., fig. 2 a). When they pass accurately through the centre of the visceral chamber, the principal or only structures observable are the tabulæ, which are complete, essentially horizontal, though flexuous, and about six in number in the space of two lines. On the other hand, when the section passes at all out of the central line of the tubes, the tabulæ are cancellated by vertical lines representing the cut edges of the septa. No mural pores have been detected.

Formation and Locality.-Abundant in the Cincinnati Group (Hudson River formation) of the Credit River, Ontario. Dr Rominger quotes the same species (under the name of C. Hertzeri, Rom.) from the Cincinnati Formation of Kentucky.

Columnaria (?) Halli, Nicholson.

(Pl. X., figs. 3, 3 a.)

Columnaria alveolata, Hall, Pal. N.Y., vol. i. p. 47, Pl. XII., figs. 1 a - c.

alveolata, Nicholson, Sec. Rep. Pal. Ont., p. 8, 1875.

alveolata, Rominger, Foss. Cor. of Michigan, p. 89, Pl. XXXIV., figs. 1, 2, and 4, 1876.

(Non Columnaria alveolata, Goldfuss.)

Spec. Char.-Corallum forming large massive colonies, which vary from a few inches to several feet in diameter, and which are composed of variously-sized polygonal corallites, in close contact with one another throughout their entire length. The walls of the corallites are not excessively thickened, and they are so completely amalgamated in contiguous tubes that even under the microscope the original line of demarcation between the tubes can be made out with difficulty or not at all. The large tubes are usually from two to three lines in diameter, though occasionally considerably more than this; and the smaller corallites are of all sizes. Septa marginal, in the form of obtuse longitudinal ridges, which vary in number from twenty to forty, do not extend to any distance into the visceral chamber, and are not divisible into an alternating longer and shorter series. Tabulæ strong, horizontal, and complete, about half a line apart or sometimes closer. Mural pores not recognised with certainty.

Obs. I have come to the conclusion, after full consideration, that the best course to adopt with regard to this species is to give it a distinct specific name, though it has so long been known to palæontologists as C. alveolata, Goldf., that this course is attended with much inconvenience, and I have myself elsewhere opposed it (Sec. Rep. Pal. Ont., p. 8). Dr Rominger has evaded the difficulty, as I tried to do, by reserving the name of C. alveolata for the form now under consideration, and by retaining Hall's Favistella stellata. It is, however, quite certain that the latter is really

the Columnaria alveolata of Goldfuss, and it is therefore best to give the present species a distinct title rather than to perpetuate a source of endless confusion. I am the more inclined to take this course, as I am disposed to doubt very strongly if the present form can be referred to Columnaria at all, and whether it is not truly a perforate coral, congeneric with Nyctopora, Nich. The material in my hands is, however, not sufficient to settle this point finally. All that I can affirm is that Columnaria (?) Halli agrees with Nyctopora Billingsii, Nich., precisely in its general form and aspect, in the complete amalgamation of the walls of the corallites, and in the fact that the septa have the form of blunt marginal ridges, not divisible into a double series. In all these points C. (?) Halli differs from the true C. alveolata, Goldf., and from the allied C. calicina, Nich. I am disposed also to think that I can detect in thin vertical sections of C. (?) Halli small mural pores, such as are so abundant in Nyctopora Billingsii. On the existence, however, of this crucial character, I must at present speak with much reserve, for the state of preservation of my specimens is such that I have not succeeded in obtaining from them any microscopic sections that could be confidently relied upon as deciding a point of such delicacy and importance. Leaving the existence of mural pores an open question, I have little to add to the above specific diagnosis of C. (?) Halli. The general form of the corallum (fig. 29) is very similar to that of C. alveolata, Goldf., though the colonies mostly tend to assume a flattened and laterally expanded form. The coralThe corallites are always polygonal and prismatic, of very un

Fig. 29.-A small colony of Columnaria (?) Halli, Nich., from the Trenton Limestone of Canada, of the natural size. (After Billings.)

equal sizes, but invariably in close contact throughout, and with

walls of no more than average thickness. Transverse sections (Pl. X., fig. 3) show that the walls are so entirely amalgamated in contiguous corallites that it is difficult to detect the original boundaries of the tubes. The same sections show that the septa are in the form of strong vertical ridges, which vary in number in tubes of different dimensions, but are invariably marginal, and never extend beyond a very limited distance into the interior of the visceral chamber. There is also no trace of that division of the septa into an alternately-disposed long and short series, such as has been seen to be so characteristic of C. alveolata, Goldf., and C. calicina, Nich.

Vertical sections (Pl. X., fig. 3 a) exhibit principally the strong, remote, and complete tabula; but when the plane of the section comes to coincide more or less closely with the plane of one of the walls of the tube, we observe also a series of vertical ridges or bands, which represent the broad edges of the septa as seen in section. In such parts of vertical sections, I think I can detect, as before said, small mural pores, but I cannot affirm this positively.

Formation and Locality.-Abundant in the Trenton Limestone of Canada and the United States. Professor Hall's specimens seem to be exclusively from the Black River Limestone, which forms an inferior division of the Trenton Limestone in the State of New York. It has not hitherto been detected in the Cincinnati formation (Hudson River Group); and this of itself is to some extent evidence of its distinctness, considering that Columnaria alveolata, Goldf. (Favistella stellata, Hall), is such a common coral in the latter formation.

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CHAPTER VIII.

SYRINGOPORIDÆ.

In the family of the Syringoporida, as typified by Syringopora itself, there is a fasciculate corallum, commencing in the form of a reticulated tubular expansion, which sends up at intervals vertical, more or less cylindrical corallites, enclosed in strong compact walls. The corallites are either completely free, as regards absolute contact, or only touch each other occasionally at limited points, and their visceral chambers communicate directly by means of hollow connecting-processes, into which the tabulæ are prolonged. Delicate spiniform septa are usually present. The tabulæ are well developed, more or less funnelshaped, and often forming an axial tube in the median line of the visceral chamber.

The type of this family is Syringopora, Goldf., which was placed by Milne-Edwards and Haime (Brit. Foss. Cor. Intr., p. lxii, 1850) with Halysites and Thecostegites in the tribe Halysitina of the family Chatetida. Subsequently, the same authors, while retaining Syringopora in the same systematic position, associated with it the additional genera Fletcheria, E. and H., and Chonostegites, E. and H. (Pol. Foss. des Terr. Pal., p. 280, 1851). The only other genera that subsequent authors have shown a disposition to associate with Syringopora are Cannapora, Hall, and Aulopora, Goldf.

Of the above genera, Halysites, Fischer, is shown conclusively, by its minute structure, to have no genuine affinities with Syringopora, and must therefore be retained in the mean