1863.] DUNCAN WEST INDIAN COKALS. 421 



species with a low septal number and fissiparous growth ; it differs 

 from that just described in its costal arrangement, but is more 

 closely allied to it than to any other Coral. 



Prom the Chert-formation of Antigua. Coll. Geol. Soc. 



6. Aste^a tenuis, spec. nov. PL XIII. fig. 11. 



Corallites close, generally cylindrical, but sometimes deformed by 

 pressure. Walls slender, distinct. Costse distinct, small, subequal, 

 well separated, sometimes inclined laterally; edges sharp. Colu- 

 mella lax, badly developed, formed of trabecule passing from the 

 ends of the septa. Septa thin, close, slender, a little thicker at the 

 wall than elsewhere, and a little larger at the columella than in the 

 middle ; they appear to have had a large tooth near the columella, 

 and are arranged in six systems, the cycles being very variable. 

 Unfortunately I have not seen any calices, and fully developed 

 corallites are also wanting. The following are the arrangements of 

 the septa in the corallites I have seen : — In one corallite there are 

 thirty septa, or three cycles, in four systems, a fourth cycle in one 

 system, and fourth and fifth orders in half a system ; in a second 

 corallite the same ; in a third, with thirty-two septa, there are three 

 cycles in four systems, and four cycles in the other two. In a 

 fourth corallite there are thirty-four septa, or three cycles in three 

 systems, four cycles in two, and fourth and fifth orders in half a 

 system. The primary septa are slightly thicker and more toothed 

 than the secondary ; and the latter are more developed than the 

 tertiary, which are rudimentary except when there is a fourth cycle, 

 and then they are as large as the secondary. The fourth and fifth 

 orders often curve towards the third. Doubtless, in well-developed 

 corallites, the fourth cycle is perfect in all the systems, being now 

 and then wanting in the half of certain systems. Endotheca ab- 

 sorbed during fossilization. Exotheca exists as cells between the 

 costse. 



Erom the Marl-formation of Antigua. Coll. GeoL Soc. Diameter 

 of the corallites about 2 lines, a little more or less. 



7. Asthma Barbadensis*, spec. nov. PL XV. figs. 6 a, 6 6. 



This Astrsean is found in the Marl-formation of Antigua, greatly 

 altered by fossilization ; the calicular surface is subplane, and the 

 calices are seen as prominent columnar casts. Coll. Geol. Soc. 



8. Astilea radiata, Lamarck, var. intermedia. 



To this variety I refer certain corals presenting the specific dis- 

 tinctions of Astrcea radiata, but having the third cycle of septa 

 complete, and a little excess of vesicular endotheca. The specimens 

 are remarkable for their varieties of fossilization, the presence of 

 crystalline quartz, as well as homogeneous flint, being common inside 

 the corallites. The variety forms a link between the great Astraeans 

 of the Miocene of the Antilles and the existing Astrcea radiata of 

 the Caribbean Sea, Astrcea, Antillarum being closely allied to it. 



* See also the Barbadian Corals, pp. 444 & 445. 



