﻿GEOLOGY AND PALEONTOLOGY OE THE CANAL ZONE. 379 



4. ORBICELLA ANTILLARUM (Duncan). 



1863. Astraea antillarum Duncan, GeuL Soc. London Quart, .lourn., vol. ]9, p. 



443. 

 18G6. Astraea antillarum Duchassaixg and Miciielotti. Sup. ( 'orall. Antilles, 



p. 86 (of reprint). 

 1867. Heliastraea antillarum Duncan, Geol. Soc. London Quart. Journ., vol. 24, 



p. 24. 

 1870. Heliastraea untillarum Duchassaing, Rev. Zooph. Antilles, p. 30. 



This coral was doubtfully referred by me ^ to the synonymy of 

 Orhicella cavernosa: but, as there is doubt, it is here accorded specific 

 treatment. 



Original description. — -"A specimen in the form of a rolled flint, 

 found with silicified wood, has the corallum large, tall, probably 

 resmbling in shape that of the San Domingan A. exothecata. Coral- 

 lites close, unequal in size, but quite distinct; the transverse section 

 shows them to be circular in outline. Septa in six systems of tliree 

 cycles. The primary and secondary septa are nearly e(iual, and reach 

 to the columella; the tertiary are small and straight; all are slender, 

 wide apart, and very (hstinct. . Costae tolerably developed, subequal. 

 Walls moderately developed, by no means strong. Columella small, 

 and occupying a small space. Endotheca greatly developed, vesicu- 

 lar, and forming cells between the septa. Exotheca well developed; 

 large cells broad, others squarer, with shelving dissepiments. Diam- 

 eter of the corallites three-tenths inch [7.5 mm.]. The interspaces are 

 filled with opalescent or porcellanous silica; sclerenchyma often 

 destroyed. Coll, Geol. Soc." 



Locality. — Montserrat. 



Duncan ^ lists a coral as Astraea antillarum. variety, and makes 

 the following note: "With more distant calices than the type, pro- 

 duced costae, and a less perfect development of the third septal 

 cycle. The exact locality is not known, but the coral, from its 

 mineralogical characters, appears to have been obtained from An- 

 tigua. Brit. Mus. " 



Regarding the apparent absence of a fom"th cycle of septa, it will 

 be noted that as they are often very small and may be broken away, 

 something especially likely to occur in worn specimens such as 

 fossils usually are, they may have been present, but were subse- 

 quently destroyed. The size of the calices, 7.5 mm. in diameter, 

 suggests the presence of quaternary septa. Additional material 

 from Montserrat is needed to solve the question. 



5. ORBICELLA ALTISSIMA (Duncan). 



1867. HdiaMrnea altisdma Duncan, Geol. Soc. London Quart. Journ., vol. 24, 

 pp. 12, 24, pi. 2, fig. 3. 



Original description.^ -'The corallum is very massive and tall, and 

 its upper surface is sub plane and wider than the bas(\ The calices 



1 Geologisch. Reichs. Mus. Leiden Samml., ser. 2, vol. 2, pt. 1, p. 2S, 1901. 



2 Geol. Soc. London Quart. Journ., vol. 20, p. 30, pi. 4, flg. 2. 



