A. JE. Verrill — Bermudian and West Indian Reef Corals. 103 



thickness according to the cycles ; those of the last cycle are very 

 thin and often bend toward and join those of the third cycle. The 

 principal septa are exsert, denticulated, and thickened at the wall. 

 The columella is usually well developed and broad. The paliform 

 teeth are distinct, but not very prominent. It sometimes forms hem- 

 ispherical masses four to five feet or more in diameter. 



This species appears to be rare at the Bermudas, and probably 

 occurs only on the outermost reefs. The only specimen seen by me 

 from there was from near the North Rocks. (Centennial collection.) 

 It is a hemisphere about 11 inches in diameter, of the typical form. 

 It is common on the Florida reefs and throughout the West Indies. 

 Bahia, Brazil; (Yale Mns.);=var. hirta, nov., with elevated corallites; 

 roughly serrate, thin costse and septa; calicles deep, 5-G'" m broad ; 

 septa narrow, perpendicular within, usually 40-44. PL xxxiii, figs. 

 2, 2a. 



Orbicella aperta Verrill. 



Heliastrcea aperta Verrill, these Trans., vol. i, part 2, p. 356, 1868. 

 Plate XXXIII. Figures 1, In. 



This species is remarkable, not only for its thin, lacerately toothed, 

 and strongly exsert septa, but also for its very thin walls and abun- 

 dant and very cellular exotheca, so that the coral is very light, as 

 compared with 0. cavernosa and 0. annularis. There are usually 

 four cycles of septa, those of the third being very narrow. 



The costa? are rather feeble and those of the fourth cycle are 

 rudimentary or lacking. 



The calicles average somewhat smaller than in 0. cavernosa, but 

 decided^ larger than in 0. annularis. They are about 6 to S mm in 

 diameter. The interseptal loculi are deep and wide. The columella 

 is rather wide, but is loosely trabecular and lamellar. 



Having recently reexamined the original type of this species, in 

 comparison with large series of O. cavernosa, I must adhere to my 

 original opinion that it is a distinct species. 



Mr. Gregory (op. cit., p. l'71) thinks it is only a form of 0. caver- 

 nosa. Mr. Vaughan (op. cit., p. •". 1) thinks it a strongly marked 

 variety, if not a distinct species. 



Both species occur on the coast of Brazil, in shallow water, and 

 apparently in the same region, but perhaps not in the same stations. 



The type was from the Abrolhos Beefs, Brazil, in three to four 

 feet of water. According to Mr. R. Rathbun, it is abundant in the 

 Bay of Bahia, as at the Island of Itaparica, where it is collected to 

 be burned into quicklime, with other corals. No. 15 is. 



