GEOLOGY AND PALEONTOLOGY OP THE CANAL ZONE. 379 



4. ORBICELLA ANTILLARUM (Duncan). 



1863. Astraea antillarum Duncan, Geol. Soc. London Quart. Journ., vol. 19, p. 



443. 

 18(30. Astraea aniillurum Duciiassaing and Michelotti, Sup. Corall. Antilles, 



p. 86 (of reprint). 

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



p. 24. 

 1870. Heliastraea arUiUarum Duchas.saing, Rev. Zooph. Antilles, p. 30. 



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

 Orbicella 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 

 i-osmbling 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 tln-ee 

 cycles. The primary and secondary septa are nearly equal, and reach 

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

 wide apart, and very chstinct. 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 thi'ee-tenths inch [7.5 mm.]. The interspaces are 

 filled with opalescent or porcellanous sihca; sclerenchyma often 

 destroyed. CoU. Geol. Soc." 



Locality. — Montserrat. 



Duncan ^ lists a coral as Astraea ardillarum variety, and makes 

 the followhig 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 fourth 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 cahces, 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. Heliastraea altissima Duncan, Geol. Soc. London Qua; t. Journ., vol. 24, 

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



Original description. — "The corallum is very massive and tall, and 

 its upper surface is subplane and wider than the base. The cahces 



1 Geologisch. Reichs. Mus. Leiden Samml., ser. 2, vol. 2, pt. 1, p. 28, 1901. 



2 Geol. Soc. London Quart. Journ., vol. 20, p. 36, pi. 4, fig. 2. 



