100 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 72 



Genus GEMELLIPORIDRA Canu and Bassler, 1927 



The ovicell is hyperstomial and is always closed by the operculum. 

 The frontal and the ovicell are covered by tremopores. The aperture 

 bears two small lateral indentations separating a very large suborbic- 

 ular anter from a very small concave poster. The operculum bears 

 two lateral marks corresponding to oral indentations and two linear 

 muscular attachments. There are two oral avicularia irregularly 

 arranged on each side of the aperture. The complete colonies are 

 multilamellar, and the zooecia are then badly oriented. 



Genotype. — GemeUiporidratypica Canu and Bassler, 1927. Recent. 



Eange. — Pleistocene. Recent. 



The other known species are : 



Gemelliporidra aculeata, new species, Recent, Gulf of Mexico. 



Gemelliporidra magniporosa, new species, Recent, Gulf of Mexico. 



Gemelliporidra {Gyclicopora) multilamellosa Canu and Bassler, 1923, 

 Pleistocene, Panama Canal Zone. 



This genus is very close to Gemellipora Smitt, 1873, in the form of 

 the operculum and of the aperture in which the lateral indentations 

 serve for the insertion of two corresponding denticles on the oper- 

 culum. It differs in a wider, rounded poster and in its larger, 

 rectangular zooecia poorly oriented (celleporine structure of Smitt) . 



As in Hippodiplosella, there are two linear bands on the operculum. 

 Gemelliporidra differs from this genus in the absence of cardelles, in 

 the presence of two indentations in the aperture, in two lateral 

 denticles on the operculum, and in the muscular attachments much 

 less clear and more irregular. The genus is known only in the 

 Tropical Zone of the Atlantic. 



GEMELLIPORIDRA TYPICA Canu and Bassler, 1927 



Plate 11, Figures 1-4, text Figures 17 a-c 



1927. Gemelliporidra typica Canu and Bassler, Classification Cheilostoma- 

 tous Bryozoa. Proc. U. S. Nat. Mus., vol. 69, p. 7, pi. 1, fig. 9. 



Description. — The zoarium is uni or multi lamellar. The zooecia 

 are large, rectangular, distinct, separated by a salient thread, oriented 

 in all directions, little elongated; the frontal is convex, formed of 

 a perforated olocyst surmounted by a granular tremocyst in which 

 the lateral pores are much larger. The aperture is suborbicular and 

 provided with two lateral indentations separating a very large anter 

 from a concave and sinuous poster. The ovicell is globular and dis- 

 posed between the olocyst and the tremocyst of the distal zooecium. 

 On each side of the aperture there is a triangular avicularium with 

 pivot, obliquely arranged, with the beak adjacent to the peristome 

 and directed towards the median zooecial axis. 



