HARD WICKE 'S S CIENCE - G OS SIP. 



221 



suddenly enlarged before and after bifurcation. 

 Dissepiments small, about one-third the transverse 

 diameter, and one-fifth the longitudinal diameter of 

 the fenestrules. Fenestrules oblong sub-quadrangular, 

 sometimes shortly spatulate or irregular near the 

 bifurcations. Cell-pores small, round, with thin 

 lips slightly raised above the surface, alternate, their 

 own diameter apart. Reverse covered by a dense 

 cortical substance, with a few scattered granules."* 



Fig. 169. Polypora tiiberculata 

 (to show arrangement of Cells). 



Fig. 170. Synocladia Sp. 

 Fenestrule to show arrange- 

 ment of pores. 



In the Scottish species "the thin lip of the pores 

 in well-prepared specimens is not circular, but sinks 

 down on the lower edge of the aperture, which thus 

 has a pyriform crater shape. In addition to the 

 ridges mentioned by Prout, the intervening surface 

 is covered with very fine short wrinkles, which are 

 sinuous, and sometimes interrupted, so as to give a 

 tubercular aspect. The fronds sometimes attain a 

 size of three inches." f 



In the building - up of its cell, this PakTeozoic 

 Polyzoan differed in some particulars as to plan from 

 its contemporaries. The pores with which its outward 

 surface was ornamented were the openings to small 

 tubes slightly incurved. These tubes had their origin 

 on the axis of the principal branches, which diverged 

 obliquely upwards on each side. Unlike Retcpora, 

 where the cells are separated one from another by 

 a thick wall, the cells of Polypora are contiguous, 

 the partition being so thin as to be inseparable under 

 an inch power. The pores in the innermost portion 

 of the branches are very much compressed into a 

 diamond shape, whereas the cells of the edges pre- 

 sent the appearance of a blown bladder, some of them 

 occupying just about double the space of the com- 

 pressed cells. It would be folly, however, to make 

 too much of this economy of space, as I observe the 

 cells in species of other genera — such as Ceriopora 

 and Glaitconome — ^of the Carboniferous era. Some 

 of the Ceriopora of the Greensand ; and Horiiera 

 reftporacea of the Crag economized in the same way. 



The other localities besides those named for Poly- 

 pora tuberailata are Loxdale Limestone and Rich- 

 mond in Yorkshire, and Hairmyres and Beith 



* Geol. Mag., June, 1874. 

 t Ibid., p. 258. 



quarries in Scotland ; for P. dendroides, M'Coy, 

 Corriebum and also Beith quarries. 



The genus Synocladia of King is not so well known 

 as many of the other forms of fenestrate Polyzoa. 

 "The 'corallum' (polyzoary) was cup-shaped, with 

 a small central root-like base, reticulated and com- 

 posed of roundish, narrow, often branched interstices, 

 bearing on the inner face from three to five alternately 

 longitudinal rows of prominent edged pores, sepa- 

 rated by narrow keels, studded with small irregular 

 vesicles, alternating with the cell-pores ; dissepiments 

 thin ; vesicles direct, usually forming short spur- 

 shaped pinnae, extending upwards from the sides and 

 meeting those from the adjoining interstices at an 

 angle directly upwards, bearing two alternate rows of 

 cell-pores. It differs from Fe/testella in the large 

 number of rows of pores in each interstice."* 



Fig. 171. Cells in dissepiment of Fig. 172. Enlarged pore of 

 Svnocladia. Polypora tubercnlata. 



'olypo 



In the Annals and Magazine of Nat. History,^ 

 Robert Etheridge, jun., has described from the 

 Lower Limestone series of Gilmerton, a most peculiar 

 polyzoon, under the name of Synocladia carbona7-ia. 

 This species agrees in its main characters with a 

 species already described by Mr. Meek as S. biserialis 

 of Swallow. J " To the latter Mr. Meek also refers 

 the Scptopora cestriensis, Prout, a form which appears 

 to differ only from the typical species oi Synocladia 

 by having from one to four rows of cell-apertures on 

 the dissepiments instead of two. On a comparison 

 of photographs of American specimens, kindly lent 

 by Professor King, all those from Scotch beds appear 

 to have a much greater irregularity of branching, and 

 there are never more than two rows of cell-apertures 

 on the dissepiments, one row on each side the keel : 

 these characters are so constant that the varietal term 

 carbonaria is here used to distinguish the American 

 and the British forms. § 



In the shales from Capelrig quarry two species of 

 Synocladia may be obtained. The other localities 

 are High Blantyre and Gillfoot in Scotland, and 

 minute fragments (?) may be found among the Carboni- 

 ferous shales of Yorkshire. 



The most delicate and beautiful of all the forms of 

 fenestrate Polyzoa that have ever come under my 

 notice is the new genus described and figured in 

 vol. 30 of the "Quart. Jour, of the Geo. Society," by 

 Professor Young and John Young, of the Hunterian 

 Museum of Glasgow. I have tried in vain to get the 

 especial part of the journal in which the description 

 is given, and to which my attention was directed by 



* " Permian Fossils." 

 t September, 1873. 

 j "Trans, of St. Louis Acad.," 1858. 



§ Robert Etheridge, jun. Expl. of Sheet 23, Scot. Geo. 

 Survey. 



