160 Vrof. H. A. Nicholson — New Devonian Fossils. 



which, so far as I am aware, presents even a superficial resemblance 

 to Botryllopora, is Evactinopora, Meek and Worthen. In this latter 

 genus, however, though the polyzoary is star-shaped, its internal 

 structure is quite peculiar and altogether diiferent from that of the 

 former, whilst the entire organism appears to have been free. 



The individual discs of Botryllopora, which, though social, are not 

 organically united, present, on the other hand, a striking resem- 

 blance to the separate star-shaped elevations of Stellipora ( Constel- 

 laria) Antheloidea, Hall, from the Lower Silurian ; and it may, 

 therefore, be proper to say a few words on the structure and affinities 

 of this fossil, of which I have examined authentic specimens. 

 Stellipora antheloidea occurs in the form of flattened expansions or 

 of erect, flattened, sub-palmate fronds. The surface exhibits a vast 

 number of little star-shaped elevations, each about a line in diameter, 

 and consisting of a smooth, sometimes slightly depressed space, which 

 is traversed by five or six obtusely-rounded radiating ridges, which 

 do not quite meet in the centre. Each of the ridges of the star is 

 covered with rounded calices irregularly disposed in three or four 

 rows. The stars are arranged irregularly, generally at intervals of 

 from half a line to a line ; and the intervals between them are 

 occupied by crowded circular pores, which are the mouths of so 

 many tubuli. These pores do not encroach upon the spaces between 

 the ridges of the stars, and the tubuli of which they are the mouths 

 are seen on transverse section to be tabulate, being furnished with 

 numerous distinct transverse partitions. It thus appears that Stelli- 

 pora antheloidea, Hall, is not a Polyzoon, as believed by D'Orbigny, 

 but, as pointed out by Milne Edwards and Haime, a tabulate coral, 

 allied to Monticulipora, and presenting in particular a close resem- 

 blance to the coral which I have described under the name of 

 Callopora incrassata. 



BoTKTLLOPOKA sociALis, Nicholson. PL IX. Fig. 16. 



Polyzoary social, consisting of systems of calcareous discs which 

 are adherent by their lower surface to the exterior of foreign bodies, 

 and which are not organically connected with one another. The upper 

 surface of each disc approximately convex, but with a central de- 

 pression or flattened space, surrounded by a series of strong obtuse 

 elevated ridges arranged in a radiating manner. The diameter of 

 the discs is about a line or a line and a half, and the radiating ridges 

 are from eighteen to twenty-six, or more, in number. The ridges 

 are unequally developed, some extending nearer to the centre than 

 others, and each carries upon its upper surface a double row of 

 minute round pores or apertures, the margins of which are not 

 elevated above the general surface. The central space of the poly- 

 zoary is destitute of cells, and appears to be solid ; and this seems 

 also generally to be the case with the spaces between the radiating 

 ridges. In some cases, however, the interradial spaces appear to be 

 poriferous in the immediate vicinity of the circumference. 



The groups of this singidar Polyzoon are not of very rare occur- 

 rence in the Hamilton Formation, growing parasitically upon the 



