252 BRITISH FOSSIL CORALS. 
discernible from the surrounding ccenenchyma. Septa 12 in number, but little developed, 
rather slender, and slightly unequal in size alternately. 
A vertical section shows that the visceral chamber of each corallite is limited by a thin, 
but well-characterised wa//, and is divided by numerous closely-set, well-developed tabula, 
that are almost all quite horizontal. The continuation of the vertical septa is often visible 
in the space comprised between the tabule. The cwxenchyma is entirely made up with 
small square cells, formed by the parieties of the vertical canalicule, and the horizontal 
dissepiments meeting at right angles. In some parts of the corallum all those small 
horizontal diaphragms comprised between two adjoining corallites are placed on the same 
level, and correspond exactly; in other parts they alternate more or less completely ; 
but in no instance do these intratrabicular dissepiments correspond with the intramural 
tabule. : 
Found in the lower Silurian deposits at Coniston, and in the upper Silurian beds at 
Wenlock Edge. Professor M‘Coy mentions its existence at Mathyrafal, Montgomeryshire ; 
High Haume, Dalton in Furness, Lancashire; Blayn y Cwm, West of Nantyre, Glyn 
Ceiriog ; and Egool, Bellaghadereen, Mayo. A variety of the same species has been met 
with by that geologist in the Bala limestone of Maes Meillion, south of Bala, Merionethshire. 
Mr. Hall has also found it in the Niagara limestone, at Milwaukie, in Wisconsin. Some 
corals from the Devonian deposits of Nehou, in Normandy, do not appear to differ 
specifically from the former. 
Specimens are in the Collections of the Museum of Practical Geology, of the Geological 
Society, of the Bristol Museum, the Parisian Museum, &e. 
HH. megastoma is easily recognised by its large and closely-set calices, and by the 
slight development of the coenenchyma. 
4. Hexiouites Gray. Tab. LVIII, figs. 1, 1a. 
Herrouires Grayi, Milne Edwards and Jules Haime, Pol. Foss. des Terr. Paleeoz. (Arch. du 
Mus., vol. v), p. 217, 1851. 
Corallum composite, dendroidal, forming lamellar sublobated expansions, both surfaces 
of which bear calices. These are placed at various distances from each other (one, two, or 
three times their diameter), and are limited by a small, well-marked, circular ridge, formed by 
the exsert edge of 12 subequal thick septa. The canalicule of the ccenenchyma are 
somewhat irregular, and their parieties are rather thick. Diameter of the calices about 
one third of a line. 
This fine fossil was found in the upper Silurian beds at Walsall, and belongs to the 
Collection of Mr. J. Gray, of Dudley. 
The remarkable frondescent form of this fossil is met with in no other species of the 
