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. 1 c). The 

 fenestrate structure of the septa is seen in a vertical section of the corallum, represented at 

 fig. 1 b. 



Breadth of the calices, nearly two fines ; 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 Pontes, 

 and that belong to the Calcaire grossier of the Parisian basin, are also referable to our 

 genus Litharsea, but all differ specifically from L. Websteri. In L. Beshayesiana} 

 L. Heberti, 2 and L. bellula? the calices are smaller, and the septa less numerous ; the 

 third cyclum, which is always complete in L. Websteri, is incomplete in the last of these 

 three species, and does not exist in the first two. In Litharaa ameliand' and L. crispa? 

 which resemble most the London Clay fossil, the walls are thinner and more prominent, 

 and the septa more echinulate. 



1 Porites Beshayesiana, Michelin, Icon. Zooph., tab. xlv, fig. 4. 



2 Litharcea 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). 



