208 BXJLLETIN 125, UNITED STATES NATIONAL. MXTSEUM. 



Measuremen ts. — 



Diameter of the peristome 0.16-0.18 mm. 



Diameter of the orifice. 0.12 mm. 



Distance between the peristomes 0.50-1 .35 mm. 



Separation of the peristomes Variable. 



Diameter of a tube O.lS-0.20 mm. 



Structure. — We have made longitudinal and meridianal sections of a number 

 of examples, all of which show the same structure. The zoarial form is a simple 

 compression without any relationship to the structure of the species. In longi- 

 tudinal section the tubes are cylindrical with peripheral gemmation, reproducing 

 at all heights. The exterior walls of the zoariiun are thick. 



The transverse section is elliptical in consequence of the compression of the 

 zoarium. The tubes here are of equal size as characteristic of cylindrical tubes. 

 The very small tubes scattered among the large ones are the tubes newly formed 

 by peripheral gemmation which have not reached their normal diameter. 



Variations. — The peristomes are not regularly placed on the zoarium; they are 

 grouped in irregular zones as in Peripora. They are little salient, but the irregu- 

 larity of the dimensions indicates the peristome was prolonged by a verj- long 

 peristomie broken bj' fossilization. 



The tube measures its greatest width in the portion where it bends away 

 from the zoarium. The tubes which appear exteriorly to arise from an imme- 

 diately inferior tube are the shorter. Those which appear to arise from before 

 the last row and which slip between the proximal peristomes are the longer. 



The ovicell located at the end of the branch is not very salient. It is hollowed 

 out of the zoarium itself, as is easy to verify in the sections. 



Affinities. — Our species is almost identical with Enfalophora capitata Robertson, 

 of whose variations we are ignorant. It differs from it in its ovicell, which com- 

 pletely covers the end of the branch, and in the smaller micrometric dimensions 

 (if the enlargement indicated on Miss Robertson's figures is exact). 



Occurrence. — Pleistocene: Santa Barbara (very common), and Dead Mans 

 Island, off San Pedro, California (rare). 



Cotypes.- Cat. No. 68758, U.S.N.M. 



