2G MADEEPORAEIA. 



Ehrenberg's Uxplanaria cincrasccns, the genus Explanaria of Ehrenberg being reserved for 

 specimens without stalks.* Tliat it is not Ehrenberg's microstoma from the Eed Sea, as 

 suggested by Dana, I should infer from the fact that its habitat is given as the Indian 

 Ocean. 



Kehberg t describes it as " one of the commonest species," occurring also at Zanzibar, and 

 often reaching " a size of 2 metres." I venture to suggest that it is only common because the 

 name has been too frequently applied. 



The figure in Ellis and Solander is somewhat puzzling. The method of growth of the 

 specimen is not clear. It can perhaps best be explained as a group of at least four cups of 

 about the same age, three at one elevation ; the fourth, behind the other three, must stand 

 on some portion of the substratum at a higher level. There are several specimens in the 

 National Collection with two young cups of about the same age and of the same species 

 growing side by side, although they do not in such cases coalesce, as they are represented to 

 have done in the figure referred to. 



Species 3. Turbinaria dansB. (PI. II. ; PL XXXI. fig. 2.) 



Description. — The original cup becomes variously modified, but is always recognisable. 

 It is generally flat and open, but may also be deep and vasiform. The cup may attain a 

 diameter of more than a foot with but slight undulations of the surface. On the other hand, 

 the folding or frilling is often very pronounced, but irregular. The folds are open, but after 

 growing taller and taller suddenly cease ; the margin tends to close round the fold and to 

 smooth out again, as if once more to try and form a horizontal cup rim. The folds are left as 

 thick conical projections, hollow underneath, within the cup. The margin is thin, and the 

 stalk short and stout. 



The corallites project from 1 mm. on even flat surfaces, to 5 mm. above the ccenenchyma 

 on the ridges of the folds. The apertures are nearly round (1"5 mm.) in the former case, more 

 oblong when situated at the top of the tall conical projections. The valleys are thickly 

 studded with minute secondary buds immersed in the ccenenchyma. 



The septa vary from 18 to 24. Their upper edges project as far as the half-radius circle, 

 and then descend sharply or with a curve to bound an elliptical fossa ; at the bottom of which 

 is a clearly defined columella surrounded by a ring of interseptal loculi nmning down all 

 round it. The interseptal loculi round the margin are sharply circumscribed, Le. they are not 

 continued into the surface furrows of the ccenenchyma, but the material separating the two 

 may be extremely thin, the iipper ridges of the septa being simply bound together peripherally 

 by very thin skeletal plates. 



The ccenenchyma is internally granular near the margin, but shows the furrows more 

 distinctly nearer the bottom of the cup. Externally it looks very solid and strong, the 

 furrows being like the more or less parallel burrowings of a minute larva in a solid substance. 



* Corallenthiere des rothen Meeres, 1834, p. 82. See further T. iMsenteriiia, synonymy, p. 57. 

 t Abh. Naturwiss. Verein Hamburg, xii. (1892) p. 44. 



