GEOLOGY AND PALEONTOLOGY OF THE CANAL ZONE. 



413 



This species is common in Pleistocene deposits near Colon, Canal 

 Zone. 



Localities and geologic occurrence. — Canal Zone stations 5850 and 

 6037; Pleistocene, Mount Hope, collected by D. F. MacDonald. 

 Throughout the West Indies, in Florida, and on the Atlantic side of 

 Central America, where there are elevated Pleistocene reefs. Now 

 living throughout the same area, in the Bermudas, the Azores (Quelch), 

 and St. Vincent (collected by Mr. Cyril Crossland, specimens do- 

 nated to the United States National Museum by Prof. J. Stanley 

 Gardiner). 



FA VIA MACDONALDI, new species. 



Plate 102, fig. 2; plate 103, fig. 1. 



Corallum massive, with a rounded upper surface (for general 

 aspect of the upper surface (see pi. 102, fig. 2). 



Calicos large, oblong, elliptical or subquadrangu^arin outline; sepa- 

 rated by intercoraUite areas from ^ to 5 mm. across. Cavities slightly 

 excavated WaPs thin on the upper edge, in places entirely composed 

 of dissepiments; deeper down fairly thick. 



Measurements, in millimeters, of calices of Favia macdonaldi. 



Calice 



Greater diameter 

 Lesser diameter. 



The number of septa in calice No. 4 of the table is about 38, of which 

 12 or 13 extend to the columella, A few rudimentary septa may have 

 been broken so as not to be distinguishable now. In calice No. 5, 

 36 septa were counted, of which about 12 extend to the columella. 

 On a polished cross section, in which every septum is clearly visible, 

 there are 31 septa in a corallite having calicular diameters of 12.5 

 and 8.5 mm.; of the septa about 12 reach the columella — that is, usu- 

 ally every alternate or every third septum extends to the columella. 

 In the calice the septa are thin and distant, but deeper down they are 

 rather thick. The inner ends of the long septa are shghtly thickened, 

 suggesting that paHform lobes were present, 



Costae correspond to all septa, greatly developed, long; those 

 from one coraUite extending to meet those from the adjacent corallite; 

 members of the different cycles subequal in thickness ; thicker in the 

 wall, gradually thinning distally. 



Columella composed of the fused inner ends of the septa; fairly 

 well developed; some papillae on upper surface. 



Thin endothecal and exothecal dissepiments well developed. 



No clear instance of asexual reproduction was observed, but that 

 it is by fission seems an inference warranted by the configuration of 

 the corallites. 



1 



2 



3 



4 



5 



6 



7 



11.5 



9.75 



10.5 



15.5 



14.5 



13 



13.5 



11.5 



8.5 



9.5 



8 



11.5 



12 



12 



