GENERA OF FA VOSITID^E, 137 



tional, or as owing its apparently massive form merely to the 

 coalescence of a succession of crusts. 



The calices of C linearis, E. and H., are very characteristic. 

 They appear as long linear slits (PL VII., figs, i-i 6), which 

 may be nearly straight, but are more commonly strongly curved, 

 and which have their margins toothed by a variable number of 

 septa (most generally two on one margin, and one on the other), 

 while they have the appearance of being embedded in a dense 

 compact ccenenchyma. The form of the calices accurately 

 expresses the form of the visceral chamber to a certain depth 

 (half a line to nearly one line) below the surface, and tangential 

 sections taken within this depth (PI. VII., fig. i c) show that 

 the tubes are still curved linear fissures, with denticulate mar- 

 gins, and surrounded by dense calcareous tissue. In the in- 

 terior of the corallum, on the other hand, the corallites appear 

 as thin-walled, subpolygonal, compressed tubes, with freely 

 open cavities. The internal structure, in fact, is precisely the 

 same as that already described as characterising C. juniperinus y 

 Eichw. Thus, sections taken at right angles to the flat surfaces 

 of the frond (PI. VII., fig. i d] show that the gently-diverging 

 and thin-walled tubes of the central area, on approaching a 

 point situated a line or less below the actual surface, suddenly 

 bend outwards, nearly at right angles to their former course. 

 They now dilate, but their central cavity, instead of under- 

 going a corresponding expansion, becomes now still further 

 restricted, and is reduced to a narrow linear chamber, which 

 occupies one side of the corallite, the whole of the remaining 

 space within the walls of the latter being occupied by a dense 

 secondary deposit of sclerenchyma. There is, however, no 

 true " ccenenchyma ; " and the appearance of such a structure 

 is only due to the deposition of this sclerenchyma in the 

 interior of the tubes, and its coalescence in contiguous coral- 

 lites, to the more or less complete obliteration of the walls of 

 the latter as recognisable structures. Lastly, sections taken 

 through the median plane of the frond, and parallel with its 



