ABT.22. CYGLOSTOMATOUS BRYOZOA — CANU AND BASSLEE. 36 



The zooecia are shorter and in the himellar forms they are detached 

 from the basal lamella at a much greater angle. This phenomenon 

 is observed frequently in the Paleozoic genera of the Order Crypto- 

 stomata and represents triparietal gemmation. 



In the cylindrical forms the zoarial axis is a long tube serving as 

 a much reduced basal lamella for all the other zooecia. This tube 

 branches many times in its length, and its ramifications themselves 

 serve as basal lamella to the adjacent zooecia. 



The dilation of the zooecial walls at their extremity has been men- 

 tioned by Pergens, 1889. In the median axis of this dilation we ob- 

 serve a soi»t of linear or moniliform canal, a lumen rather apparent 

 commimicating with the exterior. We have not had the chance to 

 observe " les petits canaux, ordinairement simples, quelquefois bi- ou 

 trifurques, traversant la partie epaissie. en rayonnant autour de la 

 cavite centrale" (pi. 6, fig. 9), noted by Pergens; probably our sec- 

 tions are not thin enough. About the central lumen we have ob- 

 served a lamellar structure slightly resembling that which Cumings 

 and Galloway have noted at the base of the acanthopores in the 

 Paleozoic genus Dehayia and analogous to that which Ulrich, 1890, 

 has figured in Khomhopo-ra. 



The funnel-shaped form of the orifice is caused by the presence of 

 a small calcareous tongue of variable size, which is often even absent. 

 It is sometimes transformed into a true perforated diaphragm 

 (^closure of Levinsen) ; the zooecia have then the aspect of the zoo- 

 ecia in the Eleidae and constitute the ectocystul zooecia of Filliozat : 

 their orifice is orbicular and not semilunar. 



The physiologic role of this tongue-diaphragm is absolutely un- 

 known, like that of the ornamented closure in the Eleidae. Perhaps 

 the tentacles were less numerous or much finer than in the other 

 species of Cyclostomata. 



The tubes of the Ceidae have therefore a very special form and 

 quite characteristic between the conical, ordinary tubes without 

 peristome and the tubes of the Eleidae. 



The ovicells have been discovered by Pergens in 1893; Canu in 

 1899 and Filliozat in 1907 have described some forms. Their nature 

 and their mode of formation classifies them among the Plagioeciidae. 

 They are not parallel to the zoarial margins, except in the case of the 

 union of many adjacent ovicells; they are more or less orbicular, 

 globular and smooth ; their contours are irregular and poorly defined. 

 The oeciostome is a very minute pore placed in the proximal region ; 

 one ovicell may bear many oeciostomes. The identity with the ovicell 

 of the genus Plagioeda is therefore not perfect, but the resemblances 

 are sufficient to justify the classification of the two in the same 

 family. 



