58 BRITISH FOSSIL CORALS. 
‘The septa are small, thin, wavy, unequal, and have very long and sharp lateral spines. 
‘The septa are in six systems, but the four cycles are incomplete. The four cycles are 
complete in two systems, but are incomplete in one of the halves of each of the other 
systems. There are therefore eight septa in two systems and six in the rest. 
The columella is small and situated deeply. 
The pali are small, and are situated before all the septa, except those of the 
last cycle. 
The coste are subequal, broad, very-slightly rounded, and barely prominent; they 
are generally marked by three rows of granules, and at the calicular margin they become 
conical, and ornamented with a prominent and wavy ridge-like process, which passes 
downwards, becoming soon lost in a faint fissure, which may be seen on most of the 
costee low down. 
Height, &ths inch. Great diameter of calice, } inch. Small diameter of calice, between 
Sths and “ths inch. 
‘This species is readily distinguished from all other striated Zrochocyathi by its shape, 
septal arrangement, small pali, and the curious ornamentation of the coste. 
Locality. Whetstone (London Clay). 
In the collection of N. T. Wetherell, Esq., F.G.S. 
These are the only Zrochocyathi which are known in the London Clay, and it is very 
doubtful if Zrochocyathus sinuosus, Brongniart, sp., was ever found there.! 
Genus—PARACYATHUS. 
1. ParacyatHus cyLinpRicus, Duncan. Plate IX, figs. 18—21. 
The corallum is cylindrical, straight, tall, and has a flat base, whose diameter is nearly 
equal to that of the corallum. ‘There is a constriction just above the base, the wall is 
often marked with growth-rings, and in some corallites the calice is slightly expanded. 
The calice is circular in outline, its fossa is shallow, and the columella very small. 
The septa are slightly exsert, and in some calices more so than in others; they are 
delicate, are marked with large granules laterally (fig. 21), and have an irregular upper 
margin. 
There are six systems of septa, and three perfect cycles; moreover, in one half of four 
or more systems a septum of the fourth cycle is developed. ‘The septal number is there- 
fore very irregular, and there are from twenty-eight to thirty septa in the calice. The 
1 See ‘Corals of the London Clay,’ MM. Edwards and J. Haime, page 22. 
