Vol. 69.] '-THE GENUS AULOPHYLLUM. 77 



Figs. '6a & 3 b. Transverse sections of a third specimen in which rejuvenescence 

 has taken place. Fig. 3 b is cut through the point corresponding to 

 E . . R iu text-fig. 8 (p. 73), and 3 a is cut about 3 aim. below that 

 point. Between 3 a and 3 b considerable reduction, both in number 

 and in length of the septal lamellae, has taken place, X 15. 

 Section illustrating stereoplasmic thickening. 

 Fig. 4. Vertical section through septa, showing the stereoplasmic thickening 

 of the septa and dissepiments in the cardinal quadrant. X 5. 

 All from Peterhill Quarry, Bathgate. 



Discussion. 



Dr. A. Vaughan complimented the Author upon the detailed 

 manner in which he had studied a group of highly-specialized 

 Clisiophyllids, and felt sure that the paper would assist materially 

 in the elucidation of many obscure points in coral-development. 

 From the excellent figures shown by the Author it appeared that, 

 as soon as any definite septal plan could be asserted, the coral 

 already possessed the essential characters of the genus. He 

 thought that the conspicuous irregularity of the very earliest 

 stages might equally well be attributed to imperfect reminiscence 

 of ancestral characters, or to mere youthful plasticity ; and he 

 considered that a great number of Aulophylla must be cut through 

 their earliest stages before the truth is arrived at. With regard 

 to the structure of the coral, from the fact that the tabula? rise at 

 the Aulopliyllum wall, he thought that it would be impossible to 

 demonstrate the continuity of the septa across that wall by hori- 

 zontal sections alone. He considered that the structures shown in 

 one figure, and said to illustrate rejuvenescence, might be explained 

 as a case of breakage followed by subsequent mending. Finally, 

 he enquired whether the Aulophylla could be employed to deter- 

 mine levels within the Yoredalian, which was a long period and 

 had as yet resisted faunal subdivision. 



The Author, in reply, stated that he was able to recognize 

 forms from D l as distinct from those which were found in the 

 Upper Dibunophyllum Zone, but could not differentiate between 

 those characteristic of D., and D 3 ; hence he was unable to use them 

 for the purpose of subdividing the Yoredales. He wished to point 

 out that he termed the stage of development B, the ' Zaphrentoid 

 Stage ' and not ' Zaphrentis Stage,' and said that he had not found 

 any stage which corresponded to Cyathophyllum. He was certain, 

 however, that the septa entered the central column in Stage C. 



"With regard to Dr. Vaughan's question concerning the possibility 

 of the corallum having been broken and then repaired, he thought 

 that the evidence pointed more strongly to the erection of a newer 

 upon an older structure. 



In conclusion, he expressed his obligations to all those who had 

 so generously placed material at his disposal, and also thanked the 

 many friends who had aided him with information and suggestions, 

 especially Mr. E. G. Carruthers, Mr. W. D. Lang, and Dr. A. Vaughan . 



