26 PEOF. P. M. PENCAN ON A NEW GENES OF MADEEPOEAEIA. 



stem explains these appearances, and it is seen that the septa are 

 really high near the axis, and narrow, and that although some 

 unite with others at the axial space of a corallite, there are 

 generally traces, and usually very definite proofs, of the presence of 

 a trabecular and non-essential columella, it often being reduced to 

 a mere lamina which is in the path of two opposed large primaries. 

 The structures at the bottom of the calices resemble a solid mass, 

 and might be taken to be very large columellas not very unlike those 

 seen in some rugose corals such as Clisiophyllum and Lonsdalia ; but 

 the true conception of the structures may be obtained by studjung 

 the sectiou of the stem and some of the newer calices at the tops 

 of the ramuscules of the upper part of the colony. The theca 

 or wall of one corallite is in contact with those of its neighbours ; 

 but fusion only occurred here and there, and, indeed, in one place 

 there are traces of very slightly projecting costse to be seen running 

 down the outer part of the walls. The union is so decided that 

 the corallites are, and always were, inseparable, and the position of 

 junction is traced by broken lines in the natural transverse section 

 of the axial corallites and by the geometrical grooves at the surface 

 of the colony. 



Gemmation is seen on the united walls of corallites, and the buds 

 have six septa : it is also observed, in the natural transverse section 

 produced by the fracture of the stem (fig. 2, d), on the surface of the 

 colony amongst the largest calices and also amongst the more rapidly 

 grown calices at the extremity of the stunted branches. Pissiparity 

 is exceptional, but occurs. 



The crossing of the calices, so generally but not universally, by 

 what appears to be a long thin septum, which consists of two 

 opposite primaries united at the axis, with or without a columella, 

 is very striking in appearance, and it is difficult to understand how 

 it or the filling-up of the axial spaces could have escaped the 

 notice of Milne-Edwards and Jules Haime ; for the structures are 

 perfectly evident in their type, which is now in the British Museum. 

 The granulation of the edges of the septa and columella and even 

 of the top of the dissepiments is most distinct and is as characteristic 

 as the linear grooves which separate, in such a geometrical manner, 

 adjacent calices. 



The colonies of this species attained a considerable size, and their 

 shape was very variable. The type of Milne-Edwards and Jules 

 Haime, now in the national collection in the British Museum, is as 

 large as a man's hand and wrist, has a more or less cylindrical 

 lower stem, which enlarges upwards, and is, as it were, compressed, 

 the surface being irregularly swollen in places and smooth else- 

 where. There are terminal, subramose, blunt-ended bran chiefs, and 

 gibbosities resembling nascent branches. In another colony the 

 shape is nearly cylindrical, and there are ill-defined gibbous swellings 

 . on it ; the size is less than that of the other. A third specimen in 

 the British Museum is a part of a very large colony which has lost 

 its branchlets and much of its main mass. The shape is like that of 

 a thick slice of bread, tall, narrow, and wide. Two of the surfaces 

 are large and broad and nearly flat, and a third or edge-surface 



