Geological Society. 235 



the differences between which and the several forms previously 

 known from various European and xlsiatic beds were pointed out. 

 The Author also called attention to the peculiar association of types 

 found in the beds of Perira Island, and to the affinities of the genus 

 Hyotherium with the recent Sus and Dicoti/les on the one hand, 

 and with the Upper Eocene Choero2)otanms on the other. 



December 1, 1886.— Prof. J. W. Judd, F.R.S., 

 President, in the Chair. 



The following communications were read : — 



1. " On a new Genus of Madreporaria — Glifphastrcea, with re- 

 marks on the Ghjphastrcea Forbesi, Edw. & H., sp., from the Ter- 

 tiaries of Maryland, U.S." By Prof. P. Martin Duncan, M.B., 

 F.R.S., F.G.S., &c. 



The specimens of Septastra'a Forbesi, Edw. & H., were examined 

 many years ago, and the Author had always a doubt about their 

 generic position. Lately a very well-preserved specimen has been 

 received, which when compared with those in the National Collec- 

 tion and carefully studied, is found to have a columella and a re- 

 markable dome of eudotheca at the top of the base of the calicular 

 fossa, resembling the well-known structure in ClisiophyUum. 



Two opposite primary septa become very narrow, extend inwards, 

 form, with another structure, a narrow linear columella, and thus 

 prodiice the appearance of a continuous lamella. The other pri- 

 maries and some of the secondary septa reach this long structure, 

 and the endotheca stretches between the ends of the septa, their 

 sides, and the columella, and closes up the interseptal loculi. The 

 epithecal dissepiments are dome-shaped at the base of the calice, and 

 are ornamented with sparsely distributed granules : superficially a 

 corresponding granulation occurs on the narrow and also on the 

 wide marginal parts of the septa. 



There is a groove between the calicos, and it corresponds with 

 the imperfect junction of the eorallite walls. Fissiparity occurs and 

 also gemmation. 



Natural sections show a narrow ribbon-shaped columella. 



The examination of the perfect specimens proves that whilst they 

 cannot be understood without sections, sections alone would never 

 enable the palaeontologist to realize the elaborate superficial struc- 

 tures. It was pointed out that weathering utterly destroyed the 

 generic and specific characters, and the Author ventured to caution 

 the students of the Madreporaria against describing weathered and 

 worn specimens of any types, and not to depend entirely upon 

 sections. 



The new genus Glypliastrcea includes Astrandag of the Goni- 

 astraeoid alliance with fissiparity, gemmation, and a ribbon-shaped 

 columella. Septastnva ForbiS^i becomes Ghipfnstnva Forbesi, 

 Edw. & H-, sp. 



