362 BULLETIN 100, UNITED STATES NATIONAL MUSEUM 



by a variable number of small salient pores. In the interior the 

 base is formed of long aborted cells with much thickened walls, 

 quite variable in form; the exterior pores are very visible. The 

 ectocyst is quite brilliant; it covers the entire organism and hides the 

 details. 



The branches are dichotomous and arranged nearly in the same 

 plane; they are developed without any regularity and without any 

 symmetry; a thick one at the side of a thin one and a young one 

 beside an old one. The principal trunk attached to the base does 

 not bear a single normal zooecium but shows on its two sides vibices 

 forming irregular polygons with 1 or 2 small pores. A little higher 

 the latter are accompanied by a true aperture. Finally the real 

 zooecia appear with their salient, separating threads. The thin 

 branches alone have zooecia with very salient and complete peri- 

 stomes. The dorsal of the branches is traversed by salient vibices 

 forming very irregular lozengeshaped areas; it is smooth, some- 

 what concave in the direction of the large axis. 



The peristomice is very thick; its anterior lip is notched by a 

 pseudorimule which terminates in a very narrow true rimule quite 

 visible in the peris tomie especially if the preparation be elevated. 

 In the interior this rimule is invisible and the aperture has the usual 

 semielliptical form of the Retepores. However, when the peri- 

 stomie is visible, it is traversed by a small, very thin, longitudinal 

 canalicule, the physiologic use of which is unknown. 



The exterior dimensions are larger than the interior in conse- 

 quence of the great thickness of all the zooecial walls. The charac- 

 teristic fissure of the ovicell in the genus Retepora is here replaced 

 by a simple canalicule which is sometimes lacking. 



Affinities. — This species appears to us rather close to Filiflustrella 

 pacifica Stoliczka, 1864, a fossil of New Zealand, in the presence of 

 two small porelike avicularia, but the illustrations are not good, 

 the magnification not being indicated. Without comparison with 

 the types it is difficult to establish a certain relationship. 



Biology. — This is a species of the great depths; it lives on the mud 

 and its large base is a necessity for their habitat without rigidity. 

 All the complicated ensemble of vibices, pores, and tuberosities 

 which decorate the base and the dorsal are probably special adap- 

 tations to bathymetric conditions; its zoarial life, the details of 

 which escape our investigations, must be very intense. We can not 

 explain especially the astonishing irregularity of the branches so 

 contrary in appearance to the most elementary rules of symmetrical 

 stability. 



These small beings secrete an enormous carapace with respect to 

 their dimensions. The peristomie is not a simple ornament but it 

 takes care of important functions as the passage of the eggs and the 



