124 PEOCEEDINGS OP THE NATIONAL MUSEUM vol.72 



drical avicularia. The aperture is elliptical, transverse; the proximal 

 rimule is very broad and of little depth. The ovicell is large, convex, 

 formed of two calcareous pellicules of which the superior is incomplete 

 and limits a large irregular frontal area. 



Measurements. — Aperturei, ^' 



^ [la = 0.10 mm. 



„ . . . ,.\Lz = 0.50 mm. v 



Zooecia (marginal)i , ^ _ ^ 



^ ^ U2 = 0.35mm. 



Afinities. — This new species differs from RTiyncliozooii vaughani 

 Canu and Bassler, 1923, from the Miocene at Bowdeu, Jamaica, in 

 its much smaller dimensions. It differs from Kkynchozoon levigatum 

 Canu and Bassler, 1923, from the Pleistocene at Mount Hope, Panama, 

 in the presence of two small pedunculate avicularia. 



Occurrence. — Pliocene: Minnitimmi Creek, Bocas Island, Almirante 

 Bay, Panama. 



Holotype.— Cat. No. 70854, U.S.N.M. 



Genus RETEPORELLA Busk, 1884 



RETEPORELLA PROMINENS, new species 



Plate 18, Figures 4-6 



Description. — The zoarium is free, arborescent; the branches are 

 compressed, elliptical in section, dichotomous, formed of four longi- 

 tudinal rows of cells. The zooecia are indistinct but slightly outlined 

 by the vibices arranged in lozenge-shaped areas. The frontal is flat, 

 finely granular. The peristomie is very salient, tubulose; the peris- 

 tome is thick, orbicular, slashed. In the peristomie there is a small 

 crown of very short and numerous spicules. The ovicell bears a 

 longitudinal fissure; it is marginated. On the dorsal the vibices are 

 arranged transversely; in the species thus outlined there are one or 

 two very small rounded avicularia. 



Measurements. — Diameter of peristome = 0.13-0.20 mm. 



Diameter of peristomice = 0.12 mm. 



Length of peristomie = 0.1 5-0.20 mm. 



ry . 1^2 = 0.75-0.85 mm. 

 Zooecia , ^ „ _ 



ife = 0.35 mm. 



We are not able to determine the true form of the aperture nor 

 that of the operculum. We have then classed this species in the 

 zoarial genus Reteporella Busk, 1884, which remains as before a 

 genus for uncertain species of this group. 



Occurrence. — Albatross Station D. 2354, east of Yucatan; 20° 59' 

 30" N.; 86° 23' 45" W.; 130 fms.; coral. 



Holotype.—C&t. No. 7578, U.S.N.M. 



