ri.ATK loS. 



FuiS. l-K). Exiti-liuerUt rngnxa, new species (p. 7;!7). 



1. Fnijiiiieiits of the zoariuiii, naturni size, as usuiilly I'ouikI. 



- I'lpper face of a reticulate and ineanilrircnui Zdariiiiii, X 8 TIm' small coiiipaiMiaents 

 act as traps for diatoms. 



3. Zoariuiii in which the ovicells are nol honlered by Hie zone of itrowlh. 



4. Fragment, X 12, showing interim- of an oviccll. 'I'lie adjacenl tnlies are arrested in 



their developmenl. 



5. Ovicelled fi'ond, X 12. The ovicell is liordered <lislallv liy llie zone of u'rnwtli. The 



oeciostome is smaller than a tuhe. 



6. FroiKl. X 12, in which the dire<-lii>n of Hie liilies has changed following a change in 



the zone of growth. 



7. A very rugose frond, X 2.5. The zone of growth is In-oken. 



S. Fragment, X 25, showing that tlie tubes begin parallel willi the toldiiig Inil llieir 

 branches are more and more diverging. The zone of growth is <|uite visihle. 



9. Specimen, X 12, with two ovicells, 'J'he position of the ovicell on the zone of growth 

 is varhihle. 



10. Longitudinal section across the lines, X 2.j. 



11. Tangential thin section, X 100. The elements are vi-ry large, hut the sirminre of I he 



tubes is identical with that of other Cyclostomata. 



12. Interior obtained by ablation of a lamella, X 2.''>. The lines of Hie peristomes are not 



in the axis of the tubes which support tliem : the latter (which appear in lozenge- 

 shape) are the branchings of the tubes which are coutiguous to the basal lamella. 



13. Tangential section of a lamella. X 2.5. 



/'/"=foia: ib, tubes developed on the basal lamella and continuing almost to the 

 zoue of growth. Their br.:nches form the rows which are thus the renniins of the 

 lilies of jieristomes (l.p.). 



14. Transverse thin section, X 25, iicrpendiciilar lo the zone ol' growth an<l cnlting only 



the tubes arranged on the liasal lamella. 1,1", — Kasal lamolla : r=fold: ;</, zone of 

 growth. 

 15, 16. Trau.sverse sections showing the tubes (/()) adjacent to the Itasal l.nin-lla (/,/<) and 

 their remifications opening on the zoarial surface and forming Hie peristoinial 

 lines (tr). 

 Vickshiirgian (Mari.-inna limestone) : One inil(> north of Monroeville, .\labania. 

 Cat. No. 0.5405, U.S.N.M. 



159 



