1863.] DUNCAN WEST INDIAN CORALS. 415 



septa are smaller than the primary and secondary ; and when there 

 are only three cycles, as in young corallites, the tertiary septa are 

 linear throughout. The quaternary septa are linear and very slightly 

 developed ; when there are more septa than those of the fourth cycle, 

 the quaternary resemble small tertiary septa. The remaining septa 

 are very small and linear, and reach a very little way from the wall ; 

 they are apt to curve towards the septa nearest them. In examining 

 the shape of the septa in this and in all the allied forms, particular 

 attention must be paid that the section is quite transverse, as any 

 obliquity will more or less alter the shape of the larger end. 



As regards the endotheca, the dissepiments are frequent and deli- 

 cate, and not very much developed. The exotheca is tolerably well 

 developed, but not in proportion to the size of the corallites. Its dis- 

 sepiments form square cells. The free surface between the costae and 

 calices has a few granules. Increase by extra- calicular gemmation. 



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



Measurements. — Diameter of the calices in six specimens | inch, in 

 seven others -| inch, and in some from \ to \ inch. The elliptical 

 calices (situated on the sides of the corallum) are about 1-j^- inch in 

 longest diameter. The greatest thickness of the septa at the wall 

 is ^j inch. Columella i inch in diameter. 



No recent specimens of this species have as yet been found, 

 and its alliances are with Astrcea Lifolensis, Edwards and Haime*, 

 and Astrcea Ouettardi, Edwards and Haime f. The latter species 

 includes also the Astrcea nobilis, Edwards and Haime; it has 

 a polygonal furrow around the calices, shallow fossae, septa exces- 

 sively thick at the wall, and indistinct walls. It has also smaller 

 corallites than the type of the new species, but larger than some of 

 the varieties ; but its costae being strong, very close, and alternately 

 very thick and thin, constitutes a specific distinction. 



A specimen of Astrcea Lifolensis (Jurassic) in the British Museum 

 has stronger resemblances to the West Indian forms than has A. 

 Guettarcli (Miocene). The general form of the fourth variety 

 (var. nobilis) differs much from that of A. Lifolensis, although there 

 is a great resemblance in their details. The costae furnish, how- 

 ever, a specific difference ; still the alliance is extremely close, 



b. Var. maonetica, PI. XIII. figs. 4 a, 4 b. 



A magnificent Astrsean, resembling the typical form, but having no 

 more than four cycles of septa. The septa are very marked, very 

 large at the wall, and resemble the printed radii on a mariner's 

 compass-card. Ccenenchyma greatly developed. The diameter of 

 the corallites is from -^ to | inch, being very variable. 



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



C. Var. PTJLCHELLA. 



Corallum large, convex, irregular in superficial outline. Corallites 

 tall, varying in diameter on account of the mode of growth, rather 

 crowded at the surface, circular in transverse section, with abundant 

 ccenenchyma. Costae wide apart. Calices rather crowded, and the 



* Polyp. Foss. des Terr. Pakeoz., 1851, p. 98. t Op. ciU p. 97. 



