ART. 14 FOSSIL AND RECENT BEYOZOA CANU AND BASSLER 101 



,, ^ A ^ \li(i — 0.22 mm. 



Measurements. — Aperturei, 



^ U(j = 0.19 mm. 



„ . [is =1.10 mm. 

 Zooecia , „ „ _ 



U2: = 0.90 mm. 



Structure. — The width of the aperture varies from 0.15 to 0.28 mm. 

 The form is orbicular, a little elongated or transverse. On the trans- 

 verse aperture two very small lateral indentations are visible as in 

 Gemellipora, but it is an exterior aspect occasioned by the presence 

 of two small cardelles. Moreover, this form is not constant and the 

 corresponding opercula are of two kinds — one is regular, the other has 

 a small lateral constriction. The opercular muscles are attached to 

 two lateral bands very close to the border. • 



The ovicell is buried on the distal zooecium and developed between 

 its oiocyst and its tremocyst; it is of the same structure as the frontal; 

 it is relatively small and closed by the operculum. On each side of 

 the aperture there is a transverse thread jointed to the salient thread 

 separating the zooecia. These threads do not limit the zooecia dis- 

 tally, although the aperture appears in a terminal projection; in the 

 interior the aperture is removed from the distal border. 



B C D 



Fig. 17.— Opercula of Gemelliporidra Canu and Bassler, 1927. A-C. Gemelliporidra typica 

 Canu and Bassler, 1927. Ordinary, elongate and transverse opercula, X 85. D, E. 

 Gemelliporidra magniporosa, new species. Two opercula showing variation, X 85. F. O- 

 Gemelliporidra aculeata, new species. F. Rare form of operculum. G. Ordinary operculum 



WITH THE thick PART OF INNER LINE INDICATING THE INSERTION OF THE OPERCULAR MUSCLES 



The frontal is a granular tremocyst; the lateral tremopores are 

 large, the others are very small. 



As in all the multilamellar species, the orientation of the zooecia 

 is not constant; sporadically inverted zooecia develop and disarrange 

 the primitive orientation. 



The avicularium is placed laterally in the vicinity of the aperture. 

 It is long, triangular, acuminated, provided with a pivot; its beak 

 is directed toward the top and toward the median axis of the zooe- 

 cium. As it is not constant, its function is only accessory; it does 

 not replace an essential organ of the zooecium itself. In spite of its 

 position, we consider it as a zoarial avicularium of oxygenation. On 



