1863.] , DUNCAN — WEST INDIAN CORALS. 417 



Costae wide apart. Exothecal cells scalariform, wider than high ; 

 from -^j to -g^- inch high, and -^ inch long. Endotheca abundant. 



This form has squarer-headed septa, longer exothecal cells, costae 

 wider apart, and a lower septal number than many of the forms of 

 the species ; and differs from the forms with three more or less in- 

 complete septal cycles in the greater thickness of the inner part of 

 the septal laminae, the broad exothecal cells, and in the disposition of 

 the tertiary septa to join the secondary. 



Prom the lithological character of the specimen thus described 

 (Coll. Geol. Soc), it is either from the Chert-formation of Antigua or 

 from the lower part of the Marl. 



g. Yar. magnifica. PI. XIII. fig. 3. 



In the smaller corallites of this variety the spear-shaped septa are 

 seen ; but in the larger, where there are from twelve to fourteen 

 septa in a system, the primary, secondary, and tertiary orders are 

 nearly equal in size. They have lost the extreme relative thickness 

 between their extremities, and, although still very thin at the 

 columella, they are not greatly developed at the wall. In some 

 corallites the septa, in transverse view, are not straight, but form 

 curving radii* ; and in all, the relation which the septa bear to the 

 interseptal spaces and to the wall is very much exaggerated. 



Corallites circular in transverse section ; they vary much in dia- 

 meter, and are now and then crowded, but generally have much 

 ccenenchyma between them. The diameters of five corallites are 

 as follows : — | inch, -| inch, 1 inch, \-fa inch, -J- inch. Walls very 

 indistinct. Costae small, and appearing to be appended to all the 

 septa. Exotheca is present, and connects the costae. Septa nume- 

 rous, especially in large corallites, where the cycles, which are small 

 and rudimentary in the lesser, become well developed. In the small- 

 est corallites there are six systems of four cycles, the fourth and 

 eighth orders being very small. In medium-sized corallites there 

 are six systems, four cycles in five systems, and in the sixth there 

 are the rudimentary sixth, seventh, and eighth orders. The first, 

 second, and third orders are nearly equal in size. In the largest 

 there are six systems, and from twelve to fourteen septa in every 

 system. Lateral teeth exist on all the primary septa at the place of 

 greatest width. The higher orders in every system are very linear. 

 Endotheca abundant, but not in excess. Columella large, well de- 

 veloped, and spongy. Ccenenchyma formed of cells produced by the 

 costae and the exothecal dissepiments. 



This is the largest form of compound Astraean yet described, and 

 when in mass must present a very striking appearance ; unfortu- 

 nately no calices have been discovered as yet. Reproduction by 

 extra- calicular budding. 



Marl-formation of Antigua. Coll. Geol. Soc, Mus. Pract. Gcol., 

 and British Museum. 



2 a. Astrjsa celltjlosa, spec, nov., typical form. PI. XIII. fig. 10. 

 Corallum tall, and, judging from the disposition of the corallites, 

 * See a specimen in the Mus. Pract. Geol. Lond. 



