﻿GEOLOGV AND TALEONTOLOGY OF THE CANAL ZONE. 363 



the fungid genus DiiHoastrea Matthai; his -4sAmea teWw/osa^ is made 

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

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

 Cyathomorpha Reuss. 



Although inadequacy of information regarding four species, 0. 

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

 Duncan, renders the preparation of an adequate synoptic table 

 impracticable, an attempt ^^'^U be made to summarize the most 

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

 larger groups: the members of the first group normally hare 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 quinary septa are present. One species, 

 OrhiceUa gahhi Vaughan, has live cycles of septa. 



SYNOPSIS OF AMERICAN SPECIES OF ORBICELLA. 



Species with 3 cycles of sepia. 



Calioes 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. limbata (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 thin. 



3.0. imperaloris, new species. 



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

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



Species of OrhiceUa vith 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) . 



Gorallites 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 thiuner and 

 taller, strongly contrast in height with the quaternaries.. 7. 0. rt/;e(7« (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. 



S. 0. bainbridgcnsis, 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, thin except in wall of some speci- 

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

 shorter than secondaries 9.0. costata (Duncan). 



1 Geol. Soc. London Quart. Journ., vol. 19, p. 417, pi. 13, fig. 10. 2 Idenx p. il9, pi. 13, fig. S. 

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



