418 PROCEEDINGS OP THE GEOLOGICAL SOCIETY. [May 6, 



subplane above. Gorallites very numerous, tall, slender, crowded, but 

 distinct ; usually cylindrical, but sometimes more or less prismatic 

 from mutual pressure ; varying in size. The transverse section of 

 the corallites is generally circular, now and then deformed. Septa 

 crowded, linear ; the primary are the largest, but often the second- 

 ary are nearly as large. The primary septa are of nearly the same 

 thickness at the wall and throughout. There are six systems of 

 four cycles; in imperfectly developed systems the fourth cycle is 

 wanting, but the persistence of this cycle throughout all the systems 

 is very generally decided. The fourth and fifth orders are very 

 small, and when there are only three cycles, the third order is small ; 

 the septa are generally straight. Columella small and slightly de- 

 veloped. The wall appears to be stout. Costae attached to every 

 septum, subequal, and not very greatly developed. Endotheca 

 vesicular, greatly developed. There are often four dissepiments di- 

 viding each interseptal space. Exotheca cellular and highly deve- 

 loped ; exothecal cells small, more rectangular and larger than the 

 endothecal cells. The reproduction is by extra- calicular gemmation ; 

 the smallest buds visible have three perfect cycles of septa. 



From the Conglomerate of Antigua. Coll. Geol. Soc. 



Dimensions. — Height of corallum several inches. Diameter of 

 corallites from 1-2 lines. 



The minute details of the structure of this Coral have disappeared ; 

 but the brilliant porcellanous silica which fills up the interseptal 

 loculi and the exothecal cells is so easily distinguished from the dull 

 colourless remains of the septa, dissepiments, and walls, that the 

 characters described are easily seen in the specimens. In some 

 parts of the specimens the sclerenchyma is whitish grey, and the 

 interspaces are filled with dark homogeneous silica, just reversing 

 the arrangement generally observed. 



The intimate relation between this form and one from a later 

 formation (the Chert) is very interesting. The latter (var. curvata) 

 has the teeth on the septa preserved ; and the septa of the third order 

 curve towards those of the second near the columella. It has all 

 the other structural peculiarities of the older form, and is clearly a 

 variety; for here and there, amongst the numerous individuals of 

 the masses from the Inclined Strata, the septa of the third order are 

 now and then seen to curve towards those of the second. 



2 b. Yar. curvata. 



Corallites slender, long, close, sometimes compressed ; circular in 

 transverse section, except when compressed. Walls thin and de- 

 licate. Costse delicate, unequal, narrow at the base, tapering ex- 

 ternally. Septa well developed, in six systems of four complete 

 cycles. The primary septa are large, toothed on either side, not 

 larger at any one point than at another. The secondary septa are 

 smaller than the primary, and have a tooth near the columella. The 

 tertiary are smaller than the secondary, vary much in size, often 

 extend nearly up to the columella, and curve there towards the 

 latter ; they have lateral teeth, and a larger tooth at the end ; or 



