1863.] DUNCAN WEST INDIAN CORALS. 435 



equal, more or less dentate projections, the small, dentate fourth and 

 fifth orders being here and there seen as rudimentary costae between 

 the larger. The tallest corallites have subequal and regular costae, 

 and the smaller corallites usually have them irregular and produced, 

 whilst those whose calices reach but a little above the coenenchyma 

 have their costae produced on its surface. The small and rudi- 

 mentary costae correspond to septa. Calices as truncated cones with 

 small blunt apertures, rather wide apart, from ^ to | inch high, cir- 

 cular at the margin, which is rather inverted ; it is also much less in 

 diameter than the corallite with its costae. Fossa shallow in some, and 

 about as deep as broad in others. Columella lax, parietal, and well 

 developed. Septa small, unequal, and much smaller than their 

 costae, barely exsert, rounded at the margin, and there a little larger 

 than elsewhere ; delicate and linear within ; in six systems of 

 usually three cycles, rarely four, occasionally the fourth cycle in half 

 a system ; the primary septa are generally the largest, the higher 

 orders are very small, and the fourth and fifth orders often incline to 

 the tertiary septa. The laminae are delicate, not cribriform, but per- 

 forated now and then, and join the columella by numerous close, 

 slightly ascending, oblique dissepiments ; they are slightly dentate, 

 and unequally granulated laterally. Endotheca but little deve- 

 loped. Exotheca close, abundant, and shelving outwards ; it is very 

 distinct on some of the produced costae. Epitheca none. Exothecal 

 dissepiments four or five in ^ inch. Diameter of the calices from 

 |to^ inch. In large specimens, here and there, the costae are 

 produced to y 1 ^ inch. 



From the tufaceous limestone of San Domingo. Coll. Geol. Soc. 



The smaller specimens of this species consist of a few corallites, 

 and the larger of tabular masses. The budding is always extra-cali- 

 cular. The truncated extremities of the cylindrical short corallites, 

 the small, dentate, rudimentary costae, and the production of the 

 larger costae distinguish this species. There are some points of re- 

 semblance to Astrcea cavernosa (recent, Antilles), Astrcea ForsJccelana 

 (recent and subfossil, Egypt and West Indies), and to Astrcea De- 

 francii (Miocene) . 



17. Sideeaste^ea ceenulata, Blainville, var. Antillaetih. 



An incrusting Coral, very short, with a slightly convex and gib- 

 bous surface. It resembles Siderastrcea crenulata in all particulars, 

 except in having a less deep calicular fossa, and the crenulations of 

 the septa most marked near the papillary columella. The septa of 

 the fourth and fifth orders turn towards and join that between them 

 at various distances from the columella, and often the fourth orders 

 appear longer than they really are. Diameter of the calices jr inch ; 

 depth of fossa -^ inch. 



Its nearest living species is Siderastrcea siderea of the Antilles, 

 and it is distant from the other American forms. 



From the Nivaje shale of San Domingo (Coll. Geol. Soc). It occurs 

 also in the Miocene of Europe. 



