48 



49. FAVOSITES FORBES: (Edw. & Haime). 



(Plate VII. Fig. 8 and PI. VIII. Fig. 4.) 



Calamopora basaltica (Goldfuss), Petref. Germ. PI. xxvi. Figs. 4 a and 4 b. 

 Favosites Forbesi (Milne Edwards and Haime), Pol. Foss des Terr. PaUoziques, p. 

 238. 



Favosites basaltica (Billings), Canadian Journal, New Series, Vol. iv. p. 106. (In part.) 



Corallum forming spheroidal, pyriform, cylindroidal, or depressed hemispheric masses, 

 composed of corallites which are generally circular or cylindrical in shape, and which are 

 usually of very unequal sizes ; mural pores usually in two alternating rows, rarely in a single 

 row ; tabulae mostly rudimentary, and represented by very close-set projecting lamellae, which 

 roughen the interior of the corallites radiating septa represented, sometimes clearly, some- 

 times indistinctly, by a number of longitudinal ridges or striae. 



The typical examples of this species are usually spheroidal, cylindroidal, or club-shaped,, 

 and possess almost perfectly cylindrical corallites. The corallites are large and small, each 

 larger one being surrounded by a ring of smaller. The larger corallites are uniformly about 

 a line and a half or a line and three quarters in diameter ; but the smaller corailites vary 

 considerably in size, from an eighth of a line up to about a line. The mural pores often can- 

 not be made Vut, but in all the specimens I have seen there are constantly two rows of pores 

 on the larger corallites, thus differing materially from F. basaltica (Gold.). Mr. Billings, how- 

 ever, states that the smaller tubes possess but a single row of mural pores. The condition of 

 the tabulae is exceedingly peculiar, and I do not think it can be due, as suggested by Mr. Bil- 

 lings, to the manner in which fossilisation was effected ; since it is constantly present in all 

 our Canadian examples of this species, whilst these occur side by side with examples of F. 

 Gothlandica in which the tabulae are complete. Exactly the same condition of the tabulae is 

 shown also in one of the figures of F. Forbesi given by Milne Edwards and Hairne, and 

 drawn from a specimen from the Upper Silurian Rocks of England. (Brit. Fossil Corals. PI. 

 60. fig. 2. f ). The tabular, namely, are present in an incomplete and rudimentary form, being 

 represented by numerous close-set lamellae, ridges, or short spines, which project a short way 

 into the interior of the corallite, giving it a most peculiar and easily recognised appearance. 

 The most perfectly preserved specimen in my possession, in which the tubes are filled up, 

 instead of being as usual hollow, exhibits tabulae which are slightly more developed than those 

 just described, approximating closely to what is observable in F. hemispherica. The tabulae, 

 namely, in this specimen are close-set, thin, flexuous lamellae, which for the most part extend 

 about half-way across the corallite, often bifurcating or interlocking at their free ends ; but 

 which, in some instances, actually become complete, and pass right across the corallite. The^ 

 radiating septa are quite rudimentary, and, when discernible at all, have the form of obscurely- 

 marked longitudinal striae. Lastly, I have observed in several specimens, especially in those 

 of a cylindroidal or clavate form, the peculiar feature that the calices of a greater or smaller 

 moiety of the colony are closed by an epitheca, closely resembling what is observed in F. tur- 

 binata (Billings). 



Mr. Billings has shown that small specimens, having the characters above mentioned, 

 pass by a perfect transition into much larger pyriform specimens, which present the peculiarity 

 that the corallites at the base of the mass are large and unequal in size, whilst those at the 

 summit are on the average smaller, and are nearly equal in size. The same eminent palaeon- 

 tologist has also pointed out that the younger pyriform colonies also pass, by an equally per- 

 fect transition into elongated cylindrical forms, often of considerable length. Both these 

 statements I am enabled to confirm from my own observation. 



Besides the typical examples of F. Forbesi which I have just described, there occur not 

 uncommonly others which I cannot at present separate from this species, though they present 

 several more or less well marked peculiarities. The corallum in the examples in question re- 

 sembles in shape the more ordinary individuals of F. Gothlandica, being circular and flattened 

 above, and springing from a pointed and attenuated base, which was doubtless enclosed in an 

 epitheca. The corallites are not distinctly circular, but are cylindroidal or sub-prismatic, and 

 they are nearly equal in size, having an average width of one line. Interspersed, however, 

 with the ordinary corallites are some smaller ones having a diameter of half a line or a little 

 less. The mural pores appear to form a double series. The radiating septa are well marked 



