CORALS OE THE LONDON CLAY. 35 



S. Nystii, 1 by its diminutive size, and by its low, very feebly-granulated septa. It is 

 worthy of notice that S. discoides is the only species of this genus that has as yet been 

 found in the Eocene formations. We have seen four specimens of this Coral ; they were 

 all met with at Haverstock Hill, and belong to the cabinet of Mr. Frederick Edwards. 



2. Genus Balanophyllia (p. hi). 

 Balanophyllia desmophylltjm. Tab. VI, figs. 1, 1 a, 1 b, 1 c. 



Balanophyllia desmophyllum, Milne Edwards and J. Haime, Monog. des Eupsammides, 



Ann. des Sc. Nat., 3 me serie, vol. x, p. 86, 1848. 



Corallum simple, adherent by a broad, incrustating basis, subturbinate, straight, rather 

 elongated, and slightly compressed. Costa almost straight, closely set, and formed of one 

 or more rows of irregular granulae ; the primary and secondary ones much taller and much 

 larger than the others, especially near the calice, and usually separated by five small ones, 

 two of which begin to appear at about two thirds down the wall, whereas the others extend 

 to the basis. Calice slightly arched, and almost elliptical ; its long axis being to the short 

 one in the proportion of 100 : 160. Calicular fossula deep and narrow. Columella 

 spongy, not highly developed, flat, and not prominent at the bottom of the calice. Septa 

 forming five cycla, usually complete ; those of the fifth cyclum more developed than those 

 of the third order, and becoming cemented together two by two beyond the inner edge of 

 those of the fourth cyclum, and constituting thus in each half system two septal laminae, 

 that in their turn unite between the inner edge of the tertiary septa and the columella. 

 In the neighbourhood of the wall, the septa of the fifth cyclum that are situated next the 

 primary and the secondary ones are cemented to them, and do not usually correspond to 

 any distinct costae ; so that in each half system there are only five costae corresponding to 

 seven septa. The large septa are terminated by an undivided edge, and are much more 

 exsert than the others ; all are thin, granulated laterally, very porous, and closely set ; 

 those of the younger orders are delicately denticulated. Height of the corallum about 



1 We have given this name to a Stephanophylha of the Antwerp Crag that we have seen in M. Nyst's 

 cabinet at Louvain, and had been referred by that author to the S. imperialis (Coquilles et Polyp, foss. de 

 Belgique, p. 633, tab. xlviii, fig. 17). This figure is pretty good, but does not show the small septa. Not 

 having described it in our Monograph of Eupsammidse, we point out here its characteristic features. The 

 under surface of Stephanophyllia Nystii, nob., is somewhat concave. The costce are of almost equal thick- 

 ness, and do not appear distinctly composed of rows of granulse ; they alternate with the well- developed septa, 

 but correspond to rudimentary septa of the sixth cyclum ; the younger ones are, as usual, united by their 

 base to the elder ones, but this apparent bifurcation takes place only very near the centre of the corallum ; 

 the intercostal furrows become gradually wider from the centre towards the circumference of the wall, and 

 are bored with pores, that, increase in size in the same manner. The calicular fossula is very deep. The 

 septa are disposed in the same way as in 5 1 . discoides and S. elegans, but are much taller, thinner, and more 

 angular ; they are denticulated externally, and present on their lateral surfaces radiate striae, which resemble 

 incomplete synapticulse ; those of the last cyclum are very small. Diameter nearly an inch ; height, 5^ lines. 



