GEOLOGY AND PALEONTOLOGY OE THE CANAL ZONE. 863 



the fungid genus Difloastrea Matthai ; his Astraea cellulosa ' is made 

 the type-species of a new genus, Antiguastrea, and his Astraea anti- 

 guensis ^ and Astraea tenuis ^ are referred to the fungid genus 

 Oyathomorp7ia Reuss. 



Althougli inadequacy of information regarding four species, O. 

 altissima, 0. antillarum, 0. insignis, and 0. intermedia, described by 

 Dunc^an, renders the preparation of an adequate synoptic table 

 impracticable, an attempt wiU be made to summarize the most 

 striking characters. With one exception, the species fall into two 

 larger groups: the members of the fii'st group normally have only 

 three cycles of septa; those of the second group have four cycles^ 

 the fourth cycle is incomplete in some specimens, while in other spec- 

 imens a variable number of quinar}^ septa are present. One species, 

 OrhicelJa gahhi Vaughan, has live cycles of septa. 



SYNOPSIS OF AMERICAN SPECIES OF OEBICELLA. 



Species uith.S cycles of septa. 



Calices usually 2 to 3 mm. in diameter; costae subequal; primary and secondary septa 

 equal, extend to the columella 1. 0. annularis (Ellis and Solander). 



Calices 3 to 4 mm. in diameter; costae usually alternately large and small; secondary 

 septa thinner than the primaries, but usually reach the columella 



2. 0. limbala (Duncan). 



Calices 3.5 to 5 mm. in diameter; costae prominent, thin; secondary septa usually 

 about half as long as the primaries, tertiaries small and thiii. 



3. 0. impemtoris, new species. 



Calices 7.5 mm. in diameter; costae tolerably developed, subequal; primary and sec- 

 ondary septa subequal, extend to the columella... 4. 0. antillarian (Duncan). 



Species of Orbicella uith the 4th cycle of septa nearly or quite complete. 



Calices 5 mm. in diameter; costae unequal, thicker than the septa, last "order-' of 



costae well developed, contrasting with rudimentary septa; septa irregular in 



arrangement, .36 in number, 6 septa in each of 6 systems. . 5.0. altissima (Duncan). 



Calices from 5 to 11 mm. in diameter; costae correspond to all septa, usually subequal; 



septa normally in 4 complete cycles, subequal over top of wall, first 3 cycles reach 



columella, no pali 6.0. cavernosa (Linnaeus). 



Costae strongly alternating in size, fourth cycle small and thin without ob- 

 vious corresponding septa 6a. var. endothecata (Duncan). 



Corallites smaller than in 6a (5 to 6 mm. in diameter), about 38 septa, last 



cycle of costae rudimentary or obsolete 66. var. cylindrica (Duncan). 



Similar to 0. cavernosa except that the first three cycles of septa are thinner and 

 taller, strongly contrast in height with the quaternaries.. 7. 0. aperta (Verrill). 

 Calices 6 to 7 mm. in diameter; costae low, equal; septa low and subequal on mural 

 summit; primaries and secondaries with rather wide erect, paliform lobes, young- 

 est septa composed of incompletely fused spines. 



8. 0. bainhridgensis, new species. 

 Calices 7.5 to 8.5 mm. in diameter; costae highly developed, alternate in size except 

 at calicular margin; septa normally in 4 cycles, tliin except in wall of some speci- 

 mens, paliform lobes and thickenings distinct but rather small, tertiaries usually 

 shorter than secondaries 9.0. costata (Duncan). 



I Geol. Soc. London Quart. Journ., vol. 19, p. 417, pi. 13, fig. 10. '- Idem. p. 419, pi. 1.3, fig. 8. 

 3 Idem, p. 421, pi. 13, fig. 11. 



