PROF. P. M. DUNCAN ON A NEW GENUS OP MADREPORARIA. 29 



the fossil which Lonsdale examined that induced him to name it 

 Columnaria, and the intercalicular groove doubtless intensified the 

 importance of the internal arrangement in his mind. Septastrwa 

 has no such dissepimental structures. 



The necessity of introducing a new genus is obvious, for the presence 

 of the structures closing the axial space, and the characters of the 

 dissepiments near and at the bottom of the calice, are of great phy- 

 siological importance. In Septastrcea proper the mesenteries would 

 have had abundance of support on the sides of the septa, and the 

 visceral cavity would have been prolonged into the axial space ; but 

 in the form under consideration there is barely any room for inter- 

 septal structures, and the nodule in the axial space would limit the 

 downward extension of the visceral cavity. It is very interesting to 

 notice a columellar structure in this Tertiary reef-builder which is 

 somewhat similar to the axial arrangement in Lonsdalia and Clisio- 

 phyllum. But the laminate columellas of those Palaeozoic forms are 

 essential and largely developed, and those of the new form are 

 comparatively insignificant ; but there is the same crowding of 

 dissepiments close to the axial space and the same apparent extension 

 of a long primary septum. 



The following is the diagnosis of the new genus : — 



Section MADKEPORAKIA APOROSA. 

 Family Astr^id^; ; alliance Goniastrceoida. 

 Genus Glyphastr^a, gen. nov. 



Colony large, subramose; corallites prismatic, more or less 

 perfectly united by their walls and having a discontinuous line of 

 separation between them ; calices polygonal and shallow, having 

 polygonal linear grooves between them, and the axial space closed ; 

 septa unequal, minutely serrate or granulate at the free edge, some 

 narrow within and long ; columella small, parietal, lamellar, or 

 ribbon-shaped, uniting opposite primaries, or several septa sometimes 

 absent, and then primary septa unite at the axial space ; endotheca 

 well developed, often simulating tabulae ; dissepiments near the 

 calice extending upwards close to the free edges of the septa and 

 columella, closing the interseptal loculi and forming with the septa 

 and columella a dome-shaped mass which projects and fills up the 

 bottom of the calicular fossa ; pali absent ; increased by gemmation 

 from the walls between the calices, and rarely by fissiparity. 



GLYPHASTRiEA Forbesi, Ed. & H., sp. ; amended. 



Colony large, with a stout stem terminating in gibbous prominences, 

 resembling aborted branchlets ; calices numerous, crowded, irregular 

 in size and shape, hexagonal, pentagonal, and even square in outline^ 

 shallow, with broad llattish margins separated by straight linear 

 shallow grooves, which form polygonal shapes around each calice ; 

 septa broad at the margin, reaching the linear groove, subequal at 

 the wall and granular there. There are three perfect cycles of septa 



