250 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



With M-all ridge on the colHne summits: 

 Valley axes narrow and deep. 



Valleys, 15 to 18 mm. wide; septa, 2 to 3 mm. apart. 



7^ lichtensteini Milne Edwards and Haime. 

 Valley axes open and shallow. 



Upper margins of the septa arched or tlattened; valleys, 16 to 20 mm. wide; 



septa, 2 to 4 mm. apart R apnia Quelcli. 



Upper margins of the septa, distally abruptly elevated; valleys, 11 to 18.5 

 mm. wide; septa, 1.4 to 2 mm. apart, occasional intermediate rudimenta- 

 ries P. gravieri, new species. 



PHYSOGYRA SOMALIENSIS, new species. 



Plate XVII. 



Apex of the base small, surmounted l)y a short, thick pedicel. The 

 lower surface more or less corrugated concentrically, ascending at a 

 low angle, with the margins in some instances slightly bent downward. 

 Cost* correspond to man}^ or most of the septa; no epitheca; wall 

 largely dissepimental in origin, often presenting a glazed appearance. 

 The reflexed edge zone may ex-tend some distance from the margin, or 

 foreign objects may incrust the base to near the periphery. The upper 

 surface is gently domed. The corallum is very vesicular and for its 



size extremely light. 



Table of measurements. 



T Figured type, Museum d'Histoire Naturelle, Paris. 



Valleys more or less radiate in arrangement; longitude, up to 120 

 mm. on specimen No. 3; distance between the summits of adjacent 

 coUines, from 11 to 18 mm,; depth, about 8 mm. Calicinal centers 

 distinct or indistinct. 



Septa thin, distant, usually alternating in prominence, the taller, 

 which are somewhat unequal, continuing to the summit of the col- 

 lines, while the smaller ones, which usually are decidedl^^ rudimentary, 

 appear farther down on the sides of the collines in the loculi between 

 the larger. There are 7 to 8 larger septa to the centimeter, and 

 approximately the same number of smaller ones. The septal margins 

 are entire; their upper portion gently arched or flattened, the outer 

 ends may connect with the septa of the next series, or they may end 

 abruptly on the colline summit; the inner margins fall abruptly to the 

 bottom of the narrow axial furrow. 



Di.ssepimental endotheca highly developed, forming vesicular ridges 

 from T.5 to 1(5. 5 mm. across; dissepiments thin, from 1 to 2 mm. 



