40 PERMIAN FOSSILS. 



resemblance to the genus Ffi/lojjora of M'Coy. These modifications are represented 

 in Plate IV, fig. 5. The bifurcation of the stems appears to be caused by the 

 addition of one or more longitudinal rows of cellules. A stem goes on increasing 

 in width for a while, through the interposition and gradual development of a new row 

 of cellules ; after which it divides : both divisions then increase in length, each one 

 afterwards dividing in the manner described. The cellules have a raised margin 

 surrounding their aperture ; and their cast shows them to be curved, overlying each 

 other, and slightly contracted at their upper part (vide diagram under figure 6, Plate IV). 

 The so-called gemmuliferous vesicles alternate with the adjoining cellule-apertures : 

 they often leave their impression in the form of a pit intervening between the rows 

 of impressed cellule-apertures, when the celluliferous surface of the fossil is in the 

 state of an impression, as exhibited in figure 4, Plate IV ; occasionally, however, a 

 specimen occurs with the celluliferous surface itself exhibited, as in figure 5, Plate IV, 

 in which case the (?) gemmuliferous vesicles are seen to be tubercular, and open at the 

 summit. Sometimes specimens are found furnished with simple root-like processes 

 on the under side of the fronds (vide Plate IV, figs, 7 and 8), similar to those already 

 noticed when describing Fenestella retiformis. 



Synocladia virgulacea is rather a common species in some localities, as at Humbleton 

 Quarry, Ryhope Field-house Farm, Dalton-le-Dale, and Hylton North-Farm. It is 

 less common at Tunstall Hill, and very rare at Whitley. In all these localities it is 

 found in the Shelly Magnesian Limestone. I found a small specimen in Breccia at 

 Tynemouth Clifi". It does not appear to have been noticed either in Germany or 

 Russia. 



Genus Phyllopora, King, 1849. 



GoRGONiA (Ehrenbekgi), Gdnitz. 

 Fenestella (Permiana = EnRENBERei), King. 



Dia(^nosis. — "A Fenestellidia consisting of infundibuliform, folded, perforated 

 fronds or fohaceous expansions. Cellules on the whole of the outer or under surface 

 of the fronds ; and planted more or less approximating to a position at right angles to 

 the plane of the capillary-tubular basal plate. Cellule-apertures with plain margins, 

 and parallel to the surface of the fronds."^ 



Type, Gorgonia Ehrenbergi, Geinitz. 



In order that the present group be properly appreciated, it has been deemed 

 necessary to make a few observations on the genus Retepora, and another one lately 

 pubhshcd in the 'Annals and Magazine of Natural History' under the name of 

 Elasmopora. Lamarck founded his Betepora on three or more species of very dissimilar 

 structure, some of which have already been made typical of other genera ; the type, 



^ Annals of Natural History, 2d series, vol. iii, p. 389. 



