M. G. Carruthers — A Revision of some Garhoniferous Corals. 71 



The differences between Z. honincJci and Z. intermedia above noted, 

 appear at first sight quite sufficient to justify the relegation of the 

 two corals to different species. But a close examination of several 

 well-preserved examples of these corals from Tournai, and especially 

 of serial transverse sections from them, in my opinion show that the 

 two are essentially identical. The differences are, in the main, 

 a matter of preservation and form of growth. The first two points, 

 i.e., the shape of the calyx and the number of septa, are not of value 

 unless dimensions are given, since they depend on the age and growth 

 of the coral. MM. Edwards & Haime do not give the dimensions 

 of Z. Iconinchi; according to M. de Koninck they are about the same 

 as those of Z. intermedia ; a very slight difference in size would account 

 for the septa being a little different in number. 



The last three points, concerning the character of the septa and the 

 fossula, are, however, of greater importance. Serial transverse sections 

 show them to depend to a great extent on the amount of stereoplasmic 

 thickening present. If this is considerable, the lobing of the major 

 septa at their inner and outer ends is emphasized, causing a close 

 fusion of the outer ends with the inner septa ; the latter consequently 

 project very slightly into the interseptal chambers, and so have 

 a rudimentary appearance in the calyx, but in the absence of thickening 

 seem long and prominent. At the same time the fusion of the inner 

 ends of the major septa with themselves and with the fossular lining 

 becomes more intimate than usual ; this, in the calyx (and it was on 

 the aspect of the calyx that the species were founded) gives rise 

 to more or less elevation in the centre of the calicinal floor, which is 

 otherwise flat. The most striking difference, however, between the 

 figured specimens of these two ' species,' lies in the shape of the fossula. 

 But this, in serial transverse sections of specimens similar to those 

 figured by de Koninck, is seen to vary to a remarkable degree during 

 the growth of the coral, and, further, like the septa, to be affected by 

 the presence or absence of accessory thickening. This is very well 

 exhibited in a t5'pical example of one of these corals from Tournai, 

 part of which is here figured (PL V, Figs. 3-3c). An examination of 

 these transverse sections shows that in its young stages there is a widely 

 expanded fossula, largely filled up by a stereoplasmic deposit 

 (PI. V, Pigs. 3«-3c). In successively higher sections this lessens, 

 the fossula then becomes constricted (PL V, Pig. 3), while in 

 the last section (not figured) it expands again internally, but 

 finally in the calyx again assumes a constricted and elongated form. 

 These sections show further that the thickening of the inner ends 

 of the major septa is quite as variable at various points of the coral's 

 growth. 



These facts clearly show that if the calyx of this particular example 

 could have been examined at various periods of growth, the coral would 

 be referred at one time to Z. honinchi, at another to Z. intermedia. 



Precisely similar appearances were afforded by similar serial sections 

 of a large number of these corals collected by Dr. Yaughan in the 

 Bristol district. It was found impossible to draw any valid distinction 

 between Z. intermedia and Z. Iconincki ; the latter name having 

 considerable priority has therefore been retained. 



