GEOLOGY AND PALEONTOLOGY OF THE CANAL ZONE. 367 



Endothecal dissepiments delicate, thin, nearly horizontal, slightly 

 inclined downward from the corallite walls. In this series of speci- 

 mens the corallite walls are thick and close together, those of ad- 

 jacent corallies sometimes being solidly fused together; usually, 

 however, there is some exotheca, consisting of stout, subhorizontal 

 dissepiments. 



Columella well developed, formed by interlacing processes from 

 the inner edges of the septa; diameter from one-third to one-half 

 that of the calice; its upper surfcce about 1 mm. below the thecal 

 margin. 



These specimens, it should be repeated, are typical, and except in 

 size and to a certain extent in the configuration of the surface show 

 almost no variation. They come from the following localities: Dry 

 Tortugas, Florida, Dr. Edward Palmer, collector, 8 specimens; east 

 end of Hog Island, Bahamas, B. A. Bean, collector, 1 specimen; 

 Florida and the Bahamas, many specimens, collected by T. W. 

 Vaughan and others. There are other specimens, bearing the in- 

 definite label "West Indies" or having no locality stated. These 

 localities indicate that the species in its typical foim is of general 

 occurrence in the coral reef areas around the Caribbean Sea and Gulf 

 of Mexico. 



The recent specimens in the United States National Museum show 

 at least four kinds of variation from the typical form. 



Variation No. 1 (pi. 84, fig. 2). — This variation is, I believe, only 

 a growth form. It, in its structural features, is the same as the 

 typical form, except that the septa near the growing edge are less 

 exsert and the exotheca appears to be absolutely solid. The corallum 

 is an obtuse, compressed column, with an undulated surface. Greater 

 diameter of the base, 62 mm.; lesser 52 mm.; height 72 mm. 



Locality. — -Dry Tortugas, Florida. 



Variation No. 2 (pi. 81, fig. 2). — -The general growth form is similar 

 to that of typical specimens, except that the surface is thrown into 

 gibbosities of irregular shape and size; these are often about a centi- 

 meter in height and several centimeters in diameter. The calices 

 are larger than in the typical specimens, often measuring 3, occa- 

 sionally 4 millimeters in diameter, between thecal summits. The 

 thecal edges are slightly elevated; the margins of the primaries and 

 secondaries decidedly exsert, not infrequently standing 2 mm. above 

 the intercorallite furrow. The three characters here mentioned are 

 the distinguishing ones of this variation, namely, gibbosities on the 

 surface; larger calices; and more exsert septa. 



Localities. — Dry Tortugas, Florida, Dr. Edward Palmer, collector, 

 1 specimen; east end of Hog Island, Bahamas, B. A. Bean, collector. 

 1 specimen; and two other specimens, without locality labels. 



