18 BRITISH FOSSIL CORALS. 



cemented to them. The sides of all the septa present granulations arranged in radiate 

 lines, but not very prominent. 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 Turbinolia humilis, whatever their size may be, for the latter 

 species is always much more cylindrical. The tertiary costee 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 costse, occupying at least one third of the height of the corallum, 

 and not corresponding to any rudiments of septa, distinguish Turbinolia Fredericiana 

 from all the other species of the same genus ; in some others, such as T. sulcata and 

 T. Boioerbanhii, the rudiments of similar costse can be seen with the help of a strong lens, 

 but these intercostal lines never become cristiform, as is the case here. The great 

 development of quaternary costse and the general form of the corallum make this species 

 have some resemblance to Turbinolia dispar; but in the latter, as well as in T. costata, there 

 is always a fourth cyclum of septa corresponding to the last cyclum of costse. It is to 

 T. Bowerbankii that T. Fredericiana approximates most ; but in the former the columella 

 is perfectly cylindrical 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 b. 



This little Turbinolia is of a much more cylindroid form than preceding species, and is 

 not so slender at its basis. The costee 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. The 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 costse 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 



1 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. 



