Geological Society. 373 



skeleton of the Chelonia ; Pliosauras shows characters resembling 

 those of contemporary Crocodilia. A third modification of the 

 Sauropterygian type is indicated by teeth and a portion of the skull 

 upon which the genus Polyptychodon has been founded. 



January 24, 1883.— K. Etheridge, Esq., F.R.S., 



Vice-President, in the Chair, 



The following communications were read : 



1. " On Streptelasma Rcemeri, sp. nov., from the Wenlock Shale." 

 By Prof. P. Martin Duncan, F.R.S., V.P.G.S. 



A great number of simple corals were found amongst the washings 

 of Wenlock Shale prepared by Mr. George Maw, F.G.S. ; and most 

 of them belong to a genus new to England, but which has been 

 observed by Messrs. Nicholson and Etheridge at Girvan. The 

 species now described is allied to the Scottish form, but differs in 

 having a fossula in the calice, a smaller septal number, and fewer 

 dissepiments and tabulae. The author described the new species 

 from sections and perfect corals, showing the great variability of the 

 septal, and the persistence of the calicular arrangement, and ex- 

 plained the remarkable method of growth by increase at certain 

 points of the calice only. He enlarged upon the variability of the 

 same coral during growth, and noticed the bisymmetry of this coral. 

 The relation of the double pinnation of the costse to the septa was 

 noticed, and also the relation of a constant vertical pair of costae to 

 tho fossula. Agreeing with Messrs. Nicholson and Etheridge upon 

 all material points regarding the diagnosis of Streptelasma, the 

 author maintained that there is a true theca with costae and not a 

 simple epitheca. With those authors he placed the genus in the 

 Zaphrentidae. The morphological data indicate that transverse sec- 

 tions of Pugose corals are apt to mislead when taken alone as fur- 

 nishing specific characters. 



2. "On CyathopJn/Uum FlttcJieri, Edw. & H., sp." By Prof. P. 

 Martin Duncan, F.B.S., V.P.G.S. 



This was a short communication explanatory of the finding of this 

 coral in the AVenlock Shale with Streptelasma Rcemeri. The author 

 referred to his essay in the i Philosophical Transactions/ 1867, in 

 which he showed that the group of Palceocycli, M.-Edw. & H., belonged 

 to the genus Cyaihophyllum — to the Rugosa and not to the Fungidae. 

 ililaschewitsch having associated the name of Kunth with that of 

 the author in proving the non-Fungoid character of the group, it 

 was explained that Kunth wrote in 1869, and that he had nothing 

 whatever to do with the original work. The author alluded to 

 his late researches into the nature of synapticulae, read before the 

 Linnean Society, and explained the probable cause of the error of 

 the distinguished French zoophytologists in their differentiation of 



Pal&ocyclvs porpita. 



