﻿306 be. a. vaughan on the pal.eontological [may i905, 



Discussion. 



The President, who said that he had, some years ago, with 

 Prof. Garwood, advocated the establishment of a Committee of the 

 British Association for the study of Carboniferous zones, welcomed 

 the Author's communication. Many years ago the late Prof. H. 

 A. Nicholson had, in conversation, suggested that corals would 

 prove useful as indices of Carboniferous zones, and it was satis- 

 factory to hear that the Author had actually found them useful for 

 this purpose. 



Prof. Garwood wished to add his congratulations to those of the 

 President, on the valuable work done by the Author for the advance- 

 ment of our knowledge of the Carboniferous succession. He was 

 struck by the difference in the fossils selected, from those charac- 

 teristic of the Settle and Shap districts ; but there seemed to be one 

 exception to this, for the occurrence of Spiriferina octoplicata in 

 the lower beds coincided with its occurrence in the Shap district. 



Mr. H. B. Woodward remarked on the great advance made by 

 the Author on the palseontological work done in the Bristol district 

 by W. W. Stoddart and others. Mr. E. B. Wethered had urged the 

 importance of the microscopic organisms in fixing horizons in the 

 Carboniferous Limestone, but they could not be very serviceable to 

 the field-geologist. With regard to the structure of the Clapton 

 district, he (the speaker) was disposed to agree with Prof. Lloyd 

 Morgan, that it was due chiefly to earth-movements. 



Dr. Bather congratulated the Author on attacking this important 

 problem in the only way that was likely to prove effective, namely, 

 by the study of the stratigrapttical relations of evolutionary series in 

 limited groups of fossils. It was, however, necessary that the 

 Author's opinions with regard to the relations of the numerous 

 forms mentioned by him should be clearly understood. For this 

 purpose his terminology should be precise. It did not seem to the 

 speaker that the Author was using the term mutation in the 

 sense ordinarily accepted by palaeontologists, or the term cir cuius 

 in the sense of its proposer, Prof. J. W. Gregory (Brit. Mus. Catal. 

 Jurassic Bryozoa, pp. 14-22). Genus connotes a genetic afnnit}^ 

 denied by Gregory to those homceomorphic assemblages for which 

 he adopted the provisional term cir cuius. 



The Bev. J. P. Blake said that he had understood that the idea 

 expressed by Prof. Gregory in the word circulus was the group 

 of specimens which approximated more or less to the type of a 

 species — like the persons who stood around a speaker, or other 

 central object, in a public place in classic times — but round whom 

 no very definite line of separation could be drawn. It was a modi- 

 fication of the old idea of a species. He understood the Author to 

 use the word in this sense, and this use, combined with the reference 

 to a single type for the central form, was very satisfactory to the 

 speaker. He had understood also the word mutation in Waagen's 

 sense, which was now well known. He regarded the paper as one 

 of considerable promise, and looked forward to great results when 



