1863.] DUNCAN WEST INDIAN CORALS. 419 



they reach only halfway, being either straight or curved. The 

 quaternary septa have wedge-shaped bases and spike-like prolonga- 

 tions, extend one-quarter the distance to the columella, and some- 

 times curve towards the tertiary. Columella lax and parietal. En- 

 dotheca greatly developed, subdividing the septal loculi by trans- 

 verse bars. Exotheca distinct, cells small. 



Dimensions. — Diameter of the corallites -J- inch ; a bud 1 line in 

 diameter has three cycles. 



Chert-formation of Antigua. Coll. Geol. Soc. As a rule, this va- 

 riety is curiously fossilized. 



3. Astr.ea Antiguensis, spec, no v. PL XIII. fig. 8. 



Corallum large, turbinate, convex and gibbous above, with a very 

 small base. Corallites long, close, rather crowded, but distinct and 

 radiating from the narrow base. ^Yalls well developed, moderately 

 thick. Costse moderately developed, projecting more than the width 

 of their base ; they are plain where seen superficially, very nearly 

 equal, and are not spined or toothed. In some corallites the fourth 

 cycle of costse is wanting, but not in those that are fully developed. 

 Calices circular, slightly raised, appearing as truncated cones, some- 

 times compressed (at the side of the corallum they are distorted), 

 unequal in size ; margin thin. Fossa not deep, but variable. Colu- 

 mella well developed, projecting at the bottom of the fossa ; its com- 

 ponent tissue is laminar and folded, and it is rounded above. 

 Septa straight, very slightly exsert, delicate throughout, not larger 

 at any point decidedly ; but the largest are more delicate midway 

 between the walls and the columella; they are arranged in six 

 systems of four cycles. The primary and secondary septa are 

 equal ; the tertiary a little smaller ; those of the fourth order are very 

 small, and barely developed in some calices, but they exist in all. 

 The primary and secondary septa have a tooth near the columella. 

 Endotheca tolerably developed. Exotheca well developed, forming 

 large and small cells, both square, though often divided by dissepi- 

 ments. Reproduction by extra-calicular gemmation. There is no 

 epitheca. 



Dimensions. — Height of corallum several inches; diameter of calices 

 from a little less than 3 lines to 4 ; thickness of septa ^ inch. The 

 dimensions of the elliptical calices are — length 3| lines, breadth 2| 

 lines, depth of fossa § line. Exothecal cells from | to | line. The 

 lateral calices are very irregular, and the younger corallites have 

 three cycles of septa. 



Fossilization. — Calices, as a rule, not filled up. Sclerenchyma 

 light-brown in colour, opaque, and siliceous, the central portions of 

 the corallum evidently consisting of dark homogeneous flint, the 

 sclerenchyma having been destroyed in the process of silicification. 



From the Marl-formation of Antigua. Coll. Geol. Soc. 



4. Aste^a endothecata, spec, nov.*, var. 1. PI. XIY. fig. 9. 

 Corallum tall, without radiating corallites, subplane above. Coral- 



* See also p. 434, amongst the Corals £ro:n San Domingo. 



