450 BULLETIN 103, UNITED STATES NATIONAL MUSEUM. 



of the corallites. The boundary between adjoining calices is formed 

 by a vertical row of synapticulae, considerably larger than the others. 



Columella papillary, fairly well developed. 



Localities and geologic occurrence. — Chattahooche formation, basal 

 part, station 3381, Little Horse Shoe Bend, Flint River, 4 miles below 

 Bainbridge, Georgia, collected by T. W Vaughan; Chattahoochee 

 formation, probably near the base, station 6084, Withlacoochee River, 

 3 miles below Valdosta, Lowndes County, Georgia, collected by L. W. 

 Stephenson; Chattahoochee formation, upper part (stratigraphicaUy 

 the same as the Tampa formation), station 3694, WaukuUa, Florida, 

 collected by T. W. Vaughan. 



Tampa formation, the '^silex'^ bed. Ballast Point, Tampa, stations 

 2115, collected by F. Burns; station 7754, an excellent specimen col- 

 lected by C. W. Cooke. 



Alum Bluff formation, station 6043 Coronet Phosphate Mine, near 

 Plant City, Florida, collected by G. C. Matson. 



Specimens of this species have been obtained at other localities in 

 Georgia and Florida in the Chattahoochee and Alum Bluff formations. 

 It is abundant around Alachua, Florida. 



Siderastrea silecensis so closely resemble S. conferta (Duncan) that 

 for some time I referred the specimens of it to that species, but in 

 calices of the same size the septa in 8. conferta are more numerous, 

 more crowded, and thinner, and have more finely dentate margins. 

 In a calice, 4.5 by 8.5 mm. in diameter, of a specimen of 8. conferta 

 from Antigua there are about 80 septa, a larger number than was 

 counted in any calice of 8. silecensis. 



10. SIDERASTREA DALLI, new species. 



Plate 119, figs. 1, la, 2. 



CoraUum forming a mass rounded above. The type has a length of 

 about 122 mm. and is 75 by 82 mm. in diameter in its median part. 



The corallites are large, hexagonal or pentagonal in shape. The 

 usual diameter is from 5 to 6.5 mm,; a large corallite is 5.75 by 8 

 mm. in diameter. Wall between the corallites usually distinct, thin. 

 Calices, shallow. 



Septa, rather thin, or fairly thick, very crowded. There are four 

 complete cycles and a fair number of the members of a fifth cycle. 

 The large calice, 5.75 by 8 mm. in diameter, has 68 septa. The 

 septal grouping need not be described, as it is that common for the 

 genus. Septal dentations fine, compressed transversely to the septal 

 planes, finely frosted, from seventeen to twenty or more teeth on the 

 members of the first cycle. No compound or double dentations were 

 seen. The septal faces, closely granulate; perforations similar to 

 those in 8. jMocenica. 



