RED SEA AND EGYPTIAN GONIOPOIivE. 108 



At the sides the walls thicken and are reticular, the reticulum being formed partly of flakes 

 bent and twisted at various angles with the surface. The radial symmetry becomes more 

 pronounced. The interseptal loculi are throughout large and open. 



The vertical section shows a very compact sheaf of perforate lamina expanding rapidly, 

 hence the mushroom shape of the stock. 



This single specimen appears in Briiggemann's MS. Catalogue as Rlwdarcea? gracilis 

 M.-E. & H. ; to which indeed it is, I think, for reasons given below, very closely allied. 



In the character of the skeleton (fig. 9) this is one of the most remarkable representatives 

 of the genus. Indeed at first sight its right to a place may be disputed. 1 have no doubt 

 myself as to its claims to be placed here. The characters are all those of Goniopora : viz. the early 

 convex growth-form, the formation of edges (in this case wide and overhanging) very common 

 in this genus, the porous walls remarkable only in the size of the pores, the fact that there 

 are more than 12 septa, the larger of which fuse to form an axial tangle with pali. This is 

 not all, we can fortunately assign a definite place to it within the genus ; it is evidently, as 

 suggested under the last heading, an extreme specialisation of the expanding sheaf formation. 

 The calicles are all formed of a sheaf of membranous walls, the septa being represented by 

 threads ; this can be seen in the section. The expansion is so rapid and marked that there 

 are no drooping edges, but the top spreads out like a mushroom. This then is to be regarded 

 as an extreme form along a definite line of growth, which fully accounts for its peculiarities. 



In addition to this specimen, there is a beach-worn pebble from some unknown locality, the 

 Alveopora cxcelsa of Briiggemann's MS. Catalogue (PI. XIV. fig. 1), which has been built out of a 

 sheaf of membranous walls, and shows signs of having once had a thick free edge. Its walls 

 and intraealicular skeleton show somewhat the same structures (PI. VIII. fig. 8) and the calicles 

 are the same size. The chief difference is in the slightly greater thickness and more laminate 

 character of the skeletal elements. Both these differences can be accounted for by the wearing 

 down of the original surface which would be thinner than the older internal skeleton. This 

 thickening of the internal skeleton is seen in the type specimen which had been split in half 

 during life. 



Hitherto no light has been thrown upon this worn pebble. It had no recorded locality and 

 its position in the coral system was a puzzle. We have now discovered that the peculiar 

 method of growth which made its generic affinities so puzzling is common to other Goniopora 

 of the Bed Sea. But, as it is a specialisation of the sheaf type of growth-form which is known 

 elsewhere than in the Bed Sea (see Table III. p. 171), there is no reason why a variation on it 

 should not also occur elsewhere ; in the meantime, however, this peculiar modification is only 

 known to occur in the Bed Sea and we can therefore provisionally refer the pebble to this 

 region. On account of the uncertainty, however, it will be mentioned again among the forms 

 from unknown localities, see p. 157, Goniopora xb. 



There are two other Corals in the collection showing much the same specialisation, one from 

 a raised beach in the Bed Sea, see G. Red Sea , and one from some unknown locality and 

 described under the heading Goniopora xe, p. 159. 



Further, there is a coral, also from the Bed Sea, photographed by Dr. Klunzinger as 

 " G. Lichen Dana," and here described under the heading " G. Red Sea 5" which appears also to 

 belong to this group. 



Lastly, the originals of Milne-Edwards' Rhodarcea gracilis in the Paris Museum are also 

 closely allied. I gather this from my notes, for the original corals reminded me of the 



