208 BULLETIN 125, UNITED STATES NATIONAL MUSEUM. 
Measurements .— 
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__ 0.18-0.20 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 zoarium 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 very long 
peristomie broken by 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 Entalophora 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. 
\ 
