18 BRITISH FOSSIL CORALS. 
cemented to them. The sides of all the septa present granulations arranged in radiate 
lines, but not very promiment. Height of the corallum two lines and a half; diameter 
of the calice one line and a third. 
Mr. Frederick Edwards, to whom we dedicate this species, has submitted to our investi- 
gation a series of young individuals, showing the changes of form produced by age. ‘The 
young Corals are rather shorter in proportion, to their breadth, than the adult ones, and 
consequently never resemble Zurbinolia humilis, whatever their size may be, for the latter 
species is always much more cylindrical. The tertiary costa make their appearance in 
T. Fredericiana when very young, but those of the fourth cyclum exist only in individuals 
that are nearly adult, 
These quaternary costa, occupying at least one third of the height of the corallum, 
and not corresponding to any rudiments of septa, distinguish Zyrbinolia Fredericiana 
from all the other species of the same genus; in some others, such as 7. sulcata and 
T. Bowerbankii, the rudiments of similar costa can be seen with the help of a strong lens, 
but these imtercostal lines never become cristiform, as is the case here. The great 
development of quaternary costa and the general form of the corallum make this species 
have some resemblance to Zurbinolia dispar; but in the latter, as well as in 7. costata, there 
is always a fourth cyclum of septa correspondmg to the last cyclum of coste. It is to 
T. Bowerbanku that 7. Fredericiana approximates most ; but in the former the columella 
is perfectly cylidrical and extremely slender, whereas in the latter it is large and 
compressed. 
Turbinolia Fredericiana has as yet been found only in the London Clay, at Barton, 
and the specimen figured in this Monograph belongs to the collection of Mr. Frederick 
Edwards. 
5. TurBINOLIA HUMILIS. Tab. II, figs. 4, 4 a, 4 6. 
D ? 
This little Turbinolia is of a much more cylindroid form than preceding species, and is 
not so slender at its basis. The coste are thin, prominent, and not closely set; the 
secondary ones begin very near the basis, and those of the third cyclum at about a quarter 
of the way up the wall. The intercostal furrows are broad, and present each a double 
row of small dimples, separated by transverse or oblique bars (fig. 4 a). The columella 
is prominent, round, and conical. he septa belong to three cycla, the last of which is 
always incomplete, and is wanting in two of the systems ;’ but it is nevertheless evident 
that the number of systems is as usual six, and not five, as would at first appear, for the 
secondary costze corresponding to the two incomplete systems begin near the basis of the 
corallum, at the same level as those of the other systems, and are as much developed as 
these, whereas they would have been much shorter, and would have began much higher 
' By an inadvertency of our artist, the third cyclum is represented in fig. 4 as if it were perfect ; 
but the specimen did not in reality present tertiary septa in more than four of the systems. 
