Boreaster. Gen. nov.
Corallum composite, massive (or thickly incrusting), made up of intimately connected polygonal corallites communicating with each other by means of mural pores. Septa in the form of longitudinal lamellæ, twelve in number. Tabulæ simple.
This genus resembles Favosites in having numerous pores in the walls of the corallites, but differs from it in the possession of lamellar septa somewhat similar to those of Columnaria, Nyctopora and Lyopora. From these three genera, however, Boreaster differs in having 12 septa only, of two alternating sizes, to a corallite. Columnaria and Lyopora are without mural pores. Nyctopora was described by Nicholson as having pores, but in well preserved specimens from the type locality, examined by the writer, mural pores were not seen; it possesses 16 septa of two orders. Boreaster and Calapœcia resemble each other in both having pores, but in the latter genus the corallites are not intimately united under any circumstances, and the septa are in the form of spine-bearing ridges.
This interesting coral may be conveniently grouped, with the Favositidæ, as its generic affinities appear to place it close to Calapœcia.
Boreaster lowi. Sp. nov.
Corallum growing in irregularly shaped masses with an unevenly undulating surface; composed of small, polygonal corallites so closely united that all trace of the line of contact between contiguous walls is apparently lost. Corallites opening at right angles to the surface, averaging about 75 mm. in diameter and generally five or six sided, as seen in transverse section, the sides of the polygons being distinctly unequal. Walls of corallites thin but less so where they bound the calyces. Septa lamallar, apparently 12 in number, of two sizes, primary and secondary, alternating, the former stout and relatively large, the latter rudimentary and observed with difficulty, especially in the calyces where the six primary septa are paramountly evident, are slightly exsert and apparently connect with the nearest and corresponding ones of contiguous corallites. Pores relatively large, oval, their greater diameter vertical, in a single longitudinal row between each pair of primary septa so as to interrupt the continuity of the secondary septa which are greatly reduced and in transverse sections are only observed in places. Tabulæ not numerous, in the form of simple, flat transverse diaphragms.
X20
The two type specimens have a maximum length of 50 and 70 mm. with a thickness or height of 25 and 30 mm. respectively.