ON THE STRUCTURE OF CARBONIFEROUS-LIMESTONE CORALS. 479 



Fifth Report of the Committee ap2)ointed to investigate the Structure of 

 Carboniferous-Limestone Corals. Draivn up by James Thomson, 

 Secretary. The Committee consists of Professor Harkness, F.R.S., 

 James Thomson, F.G.S., Dr. Duncan, F.R.S., and Thomas 

 Davidson, F.R.S. 



During the past year the Committee have continued their investigations with 

 increased interest. Indeed the longer they continue their investigations in 

 this branch of pala3ontology, the more they are impressed with its importance ; ' 

 and now that they can reproduce in facsimile the internal structures of fossil 

 corals, they hope that the British Association wiU be convinced of the pro- 

 priety of continuing these researches. 



Within the period embraced by the Report upwards of 200 specimens have 

 been sliced ; these are from a locality in Fifeshire, which had escaped our 

 notice. Many of these specimens, in addition to confirming the discovery of 

 new forms (noticed in a previous Eeport), exhibit structural characteristics 

 that warrant us in determining two (if not three) new genera. 



There are others figured this year in Plates*, upon which we at present 

 hesitate to decide. They require careful comjjarison before we can feel con- 

 fident of the group in which they must be classed. 



In the Eeport of last year it was stated that the gradations of varieties are 

 in some cases so constant, and the species pass so imperceptibly into each 

 other, that we are induced to infer that there has been an inherent tendency 

 in the polyp to vary independent of, but modified by, the conditions of its 

 surroundings. It was also stated that it was our intention to figure these 

 variations, so as to enable us to see what are the essential characteristics that 

 distinguish the species. We have accordingly prepared six Plates and figured 

 284 forms, showing in each case the internal structure. The external aspect 

 is also represented when necessary. 



We have deferred to another occasion our treatment of such forms as 

 Beamnontia, Alveolites, Favosites, &c. Some palajontologists have doubts as to 

 whether several genera should be retained among the Eugose Corals, so that 

 we are the more induced to delay dealing with several forms belonging to 

 this group ; and we feel convinced that our future researches will bring to 

 light specimens simpler in organization, but presenting new facts which may 

 cause considerable alteration in the classification of this group. It is better, 

 therefore, to wait until these distinctive characteristics are clearly brought 

 out. We have, however, given in (what we provisionally call) Plate I. some 

 forms which are closely allied to the above. 



Plate I. contains twenty-three figures of the genus Amplexus. Ten of these 

 forms have not been recorded before, whilst others are now for the first time 

 recorded as occurring in British strata. These figures represent the develop- 

 ment of coralline life, passing from the simplest forms to the more complex 

 structures of the genus, which passes by imperceptible gradations into the 

 genus Zaphrentls. Prof. De Koninck finds a similar transition in the Moun- 

 tain-Limestone Corals of Belgium belonging to this genus (Eecherches sur les 

 Animaux Fossiles Belgique, prem. part. p. 81). 



Pigs. 22, 23, 25, 26, 28, 30, 31, and 32 have not been represented before, 

 and their structural characteristics are distinctly different from any of the 

 forms that have hitherto been described. 



Plate II. contains sixty-six figures ; twenty-one of these are varieties of 



* The Plates referred to in this Eeport will be publisied by Mr. Thomson. 



