384 BULLETIN 103, UNITED STATES NATIONAL MUSEUM. 



been characterized by Milne Edwards and Hainie as having but 

 three cycles." 



Lamarck's Astrea argus is a new name for the Madrepora cavernosa 

 Esper. The reason for his giving it is not evident. 



The specimen identified by Ehrenberg as Explanaria argus, which 

 is the type of Milne Edwards and Haime Astrea conferta, is in the 

 Berlin Museum fur Naturkunde, and the following notes are based 

 upon it: 



The specimen is much worn and is apparently somewhat fossilized. 

 The calices are not regularly rounded, but frequently are of irregular 

 polygonal outline. The greater diameter of an average calice is 

 8.5 mm.; lesser 7 mm. Thickness of wall between the calices is 2.5 

 mm. In one calice there were 21 large and 21 smaller septa; there 

 may be four complete cycles in some calices. The columella is very 

 large and vesicular and occupies the greater part of the oorallite 

 cavity. Dissepiments abundant, about 13 to 5 mm.; they slope 

 downward and inward. From reading the Pourtales description 

 quoted above, it will be evident that this is only a variety of 0. 

 cavernosa with crowded calices. The Explanaria radiata of Ehrenberg 

 is the ordinary Heliastraea cavernosa as figured by Milne Edwards 

 and Haime, except that the fourth cycle of septa may not always be 

 complete. 



Orbicella cavernosa var. compacta Vaughan (pi, 88, figs. 3, 3a, 3b) 

 has solid exotheca, low mammillate coraUites, and equal costae. 

 Recent on the Brazilian coast; lat. 12° 48' S., long. 38° W.; 27 

 fathoms. 



Localities and geologic occurrence. — On the living and Pleistocene 

 reefs of Florida, the West Indies, and the Caribbean side of Central 

 America. There are beach worn or Pleistocene specimens from the 

 Isthmus of Darien in the United States National Museum, collected 

 by Dr. Van Patton. 



6a. ORBICELLA CAVERNOSA var. ENDOTHECATA (Duncan). 



Plate 89, figs. 1, la. 



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



p. 434, pi. 15, figs. 7a, 7b. 

 1868. Heliastraea endothecata Duncan, Geol. Soc. London Quart. Journ., vol. 24, 



p. 24. 



The corallite walls are thick; costae strongly alternating in size; 

 the last cycle are small and thin, and there appear to be no septa 

 corresponding to them; occasionally there is a rudimentary septum 

 of the fourth cycle. The last cycle of septa may have been broken 

 off; or the wall, because of subsequent thickening, may have included 

 their inner ends; all other septa, with rare exceptions, extend to the 

 large, well developed columella. Diameter of corallites from 8 to 



