Frof. H. A. Nicholson — New Devonian Fossils. 161 



exterior of HeliopliyTlum Halli. It has, at first sight, a close re- 

 semblance to a group of little discoid corals, such as Microcyclus, 

 attached by the whole of the lower surface ; the radiating ridges 

 looking like the septa, and the central space representing the calice. 

 I do not know of any Palaeozoic forms of Polyzoa with which the 

 present species could be compared ; and it is readily separated from 

 such forms as Defrancia by the entii'ely different characters of the 

 cells, which approach closely in form to those of Eetepora, Fenestella, 

 and Polypora. The largest group that has come under my notice 

 comprises about twenty of the discoid coenoecia, mostly in contact, 

 but apparently in no way connected with one another directly. 



Locality and Formation. — Hamilton Formation, Bartlett's Mills, 

 near Arkona, Bosanquet. 



Ceriopoka (?) Hamiltonbnsis, Nicholson. PI, IX. Fig. 17. 



Polyzoary ramose ; branches cylindrical, about half a line in 

 diameter, dividing dichotomously at intervals of from a line and a 

 half to three lines, the angle included between each pair of branches 

 being from 40° to 45°. Surface covered with oval, rounded, or sub- 

 quadrate cell-mouths, arranged in longitudinal rows, which are sepa- 

 rated by delicate thread-like lines or ridges. The cells of contiguous 

 rows alternate, so that the apertures come to be also disposed in 

 regular diagonal lines. About four rows (sometimes five) occupy 

 the width of the stems, the cells having a width of about a tenth of 

 a line. About five cells occupy the space of one line measured 

 vertically. The interspaces between the mouths of the cells are 

 occupied by exceedingly minute tnbuli, which form only a single 

 row, or are altogether absent on the lines which bound the cells 

 laterally, whilst they usually form a double series on the spaces by 

 which the cells of a given row are separated vertically. 



This beautiful little fossil occurs in great abundance in some of 

 the beds of the Hamilton formation. It is allied to the Ceriopora 

 punctata of Goldfuss (Petref Germ, plate Ixiv. fig. 12), and 

 to Millepora interporosa, Phillips (Geology of Yorkshire, vol. ii. 

 pi. i. figs. 36-39), especially to the former; but it is distinguished 

 from both by perfectly good and easily recognized characters. I am 

 at present unable to decide as to its true generic affinities, and have 

 simply referred it provisionally to Ceriopora on account of its close 

 relationship to G. punctata, Goldf., which likewise occurs in the 

 Devonian Rocks. 



Locality and Formation. — Common in the Hamilton Formation, 

 Widder, Township of Bosanquet. 



PoLYPOKA puLCHELLA, Nicholson. PL IX. Fig. 18. 

 Polyzoary infundibuliform or flabellate, often of considerable size. 

 Branches nearly straight, radiating from the base, and increasing in 

 number hj bifurcation at intervals of from two to four lines. About 

 six branches in the space of three lines, the diameter of the branches 

 being rather more than a quarter of a line, and the interspaces 

 slightly less. Dissepiments on the same plane as the outer surface 

 of the polyzoary, depressed below the inner surface, short, narrower 



DECADE II. — VOIi. I. — NO. IV. .11 



