CORALS OF THE LONDON CLAY. 39 
of a spongy texture, not projecting at the bottom of the fossula, and terminated by a 
somewhat papillose surface. Septa thin towards the columella, thick externally, strongly 
echinulated laterally, broad, closely set, not exsert, terminated by an oblique crenulated 
edge, and forming three complete cycla, besides which there is sometimes a very 
incomplete fourth cyclum. The secondary septa differ but little from those of the first 
order ; the tertiary ones also well developed, bent towards those of the second cyclum, and 
cemented to them along the inner edge near the columella. A horizontal section shows 
that the visceral chamber is cylindroid at some distance from the calice, and that the 
spongy tissue of the walls and the columella becomes much developed (fig. 1c). The 
fenestrate structure of the septa is seen in a vertical section of the corallum, represented at 
fig. 1 4. 
Breadth of the calices, nearly two lines; depth, half a line. 
This fossil is very abundant at Bracklesham Bay. The specimens from which we have 
drawn up the preceding description belong to the collections of the Geological Society, 
of Mr. Bowerbank, Mr. F. Dixon, and Mr. Frederick Edwards. 
Some other Corals that have been described under the names of Astrea or of Porites, 
and that belong to the Calcaire grossier of the Parisian basin, are also referable to our 
genus Litharea, but all differ specifically from LZ. Wedsteri. In L. Deshayesiana,' 
L. Heberti and L. bellula,* the calices are smaller, and the septa less numerous ; the 
third cyclum, which is always complete in L. Wedster?, is incomplete in the last of these 
three species, and does not exist in the first two. In Litharea ameliana' and L. crispa,’ 
which resemble most the London Clay fossil, the walls are thinner and more prominent, 
and the septa more echinulate. 
1 Porites Deshayesiana, Michelin, Icon. Zooph., tab. xlv, fig. 4. 
2 Litharea Heberti, nob. This undescribed species presents the following characters: Corallum 
composite, convex, massive, and often formed of superposed layers. Common epitheca moderately developed. 
Walls scarcely distinct. Calices polygonal and shallow. Columella not well developed, and appearing to 
be formed only by the inner marginal denta of the septa. Septa not exsert, very thick, especially outwardly, 
strongly echinulated laterally, terminated by an almost horizontal, spinular edge, and forming only two 
cycla. The twelve septa are nearly equal in size, and of a very porous structure; the spiniform granula- 
tions which cover their lateral surfaces are so highly developed, that they often become united to those of 
the neighbouring septum. This fossil has been found in an excellent state of preservation at Auvert, by 
M. Hebert, and appears to be specifically identical with same dilapidated corals met with at Valmondois. 
3 Astrea bellula, Michelin, op. cit., tab. xliv, fig. 2. 
4 Astrea ameliana, Defrance ; Astrea muricata, Goldfuss, Petref. Germ., vol. i, tab. xxiv, fig. 3. 
5 Astrea crispa, Michelin, loc. cit., tab. xliv, fig. 7; (but not the Astrea crispa of Lamarck). 
