364 BULLETIN 103, UNITED STATES NATIONAL MUSEUM. 



Oalices 5 to 9 mm. in diameter; costae subequal or alternately large and small below 

 calicular edge . Septa in 4 or nearly 4 complete cycles ; primaries as a rule notably 

 larger than the secondaries, with a prominent tooth on inner end; secondaries 

 smaller, but with paliform tooth on inner end of each; tertiaries still smaller; 



quaternaries very small 10. 0. canalis, new species. 



Calices 6 to 10 mm. in diameter, exsert 4 to 4.5 mm.; costae very prominent, no or 



only rudimentary costae correspond to last cycle of septa; septa in 3 or 4 sizes, 



margins of primaries exsert as much as 1.5 mm. .. 11. 0. tampdensiss, new species. 



Calices not so elevated as in 11; small but distinct costae correspond to last 



cycle of septa 11a. var. silecensis, new variety. 



Calices 5 mm. in diameter, protuberant but rather low; costae strongly alternating 

 in size; primary septa the largest; fourth cycle incomplete 



12. 0. brevis (Duncan). 



Calices 10 mm. in diameter; costae long, slender, subequal, occasionally a rudimentary 



costa with no corresponding septum; septa delicate, long, slender, distant, fourth 



cycle incomplete 13. 0. insignis (Duncan). 



Calices 5 mm. in diameter; in places small costae between larger ones; a few qua- 

 ternary septa 14. 0. intermedia (Duncan). 



The numbers preceding tlie names in the synopsis correspond to 

 numbers before the names heading the following descriptions. 



As OrhiceTLa gabhi is the only species with 5 complete cycle of septa, 

 it needs no special caption nor is 0. irradians included in the key. 



1. ORBICELLA ANNULARIS (ElUs and Solander). 



" Plate 80, figs. 7, 7a, lb; plate 81, figs. 1, la, 2; plate 82, figs. 1, la, 2; plate 83, figs. 

 1, 2, 3, 3a; plate 84, figs. 1, 2, 3, 3a. 

 1786. Madrepora annularis Ellis and Solander, Nat. Hist. Zooph., p. ]69, pi. 53, 



figs. 1, 2. 

 1786. Madrepora faveolata Ellis and Solander, Nat. Hist. Zooph., p. 166, pi. 53, 



figs. 5, 6. 

 1790. Madrepora acropora Gmelin, Linn. Syst. Nat., ed. 13, p. 3767. 

 1790. Madrepora faveolata Gmelin, Linn. Syst. Nat., ed. 13, p. 3769. 

 1794. Madrepora acropora Esper, Pflanzenth., Fortsetz., vol. 1, p. 21, pi. 38. 

 1'816. Astrea annularis Lamarck, Hist. nat. Anim. s. Vert., vol. 2, p. 259. 

 1821. Astrea annularis Lamouroux, Exp. Meth. Genres des Polyp., p. 58, pi. 53, 



figs. 1, 2. 

 1821. Astrea faveolata Lamouroux, Exp. Meth. Genres des Polyp., p. 58, pi. 53, 



figs. 5, 6. 

 1834. Explanaria annularis Ehrbnberg, Corallenth. Roth. Meer., p. 84 (of 



separate). 

 L846. Astraea {Orbicella) annularis Dana, U. S. Expl. Exp, Zoophytes, p. 214, 



pi. 10, fig. 6. 

 1857. Heliastraea annularis Milne Edwards and Haime, Hist. nat. Corall., vol. 



2, p. 473. 

 1861. Heliastraea annularis Duchassaing and Michelotti, Mem. Corall. Antilles, 



p. 76 (of reprint). 

 1861. Heliastraea acropora Duchassaing and Michelotti, M^m. Corall. Antilles, 



p. 76 (of reprint). 

 1861. Heliastraea lamarchi Duchassaing and Michelotti, Mem. Corall. Antilles, 



p. 76 (of reprint). 

 1863. Cyphastraea costata (part) Duncan, Geol. Soc. Lond. Quart. Joiu-n., ^'ol. 19, 



pp. 441 and 443. 

 1863. Astraea barbadensis Duncan, Geol. Soc. Lond. Quart. Journ., vol. 19, pp. 



421 and 444, pi. 15, figs. 6a, 66. 



