46 PERMIAN FOSSILS. 
concluded to be the homologues of the gemmuliferous vesicles often seen overlying the 
cellule-apertures of Bryozoic Corals. 
As the mode of formation of the gemmuliferous vesicles is not generally known, a 
few particulars on the subject, as supplied by an examination of some recent forms, 
may not be altogether inappropriate. In Hasmopora (Beaniana) they are prominent 
and spherical: their basal or attached portion, somewhat cup-shaped, is first formed; next 
their lateral margins, which arch over to within a short distance of each other, leaving 
a narrow longitudinal fissure. In Hscharina the vesicle in its early stage resembles the 
latter; its lateral margins, however, do not remain separated, but become confluent, 
forming an irregular dome-shaped appendage: whether the foramina with which its 
outer or convex wall is furnished, answer the purpose of an opening, or there is one on 
its proximal or inferior part, that is, m proximity to the upper lip of the cellule- 
apertures, [am not enabled to say. In Cellaria salicornia the gemmuliferous chamber 
is neither prominent nor spherical, but always remains sunk in the substance of the 
Coral, forming a cup-shaped cavity, as it evidently is in Zhamniscus dubius: at first 
there is a difficulty in distinguishing it from the adjacent inferior cellule-aperture ; 
afterwards, however, it becomes gradually separated from the latter by the interposition 
of a narrow calcareous dissepiment ; and its opening, at first circular, is gradually 
converted into a transverse linear fissure. 
Besides the gemmuliferous chambers in 7iamniscus dubius, but where they are 
absent, there is occasionally seen what may be termed an accessory vesicle on both sides 
of the distal lip of the cellule-apertures, as represented in Plate V, fig. 11 @, which 
reminds one of a similar structure a little below and on both sides of the proximal 
lip of the cellule-apertures in certain Escharinas. 
In some specimens of Zhamniscus dubius, as in the one represented under figure 12, 
Plate V, the proximal lip is furnished with a denticle-like process, which occasionally 
varies a little between the right and left of its usual position.’ In a few instances I 
have observed casts of the same appendage, showing it to have been hollow, and 
homologous with the hollow mucronate process similarly situated in Cellepora Skenet, 
in which the mucro is furnished with two foramina on the upper side and near the 
base. Hlasmopora Beaniana possesses a similar process, but it is foraminated at 
the point. I have not been able to discover, as yet, any foramina in the corresponding 
part of the fossil. 
The first synonym quoted for this species is explained by the fact, that Schlotheim 
imagined its branches to be the arms of a Cyathocrinus ramosus incrusted with 
a Thamniscus dubwus. 
Thamniscus dubius is not a common Coral, though it is pretty generally distributed. 
It occurs at Tunstall Hill, Ryhope Field-house Farm, Castle Eden Dene, Humbleton 
! In the impression of the fossil represented in Plate V, fig. 11 e, there is a pit or depression of the 
same appendage under some of the cellule-apertures. 
