54 PROCEEDINGS OF THE NATIONAL. MUSEUM vol.67 



PLETHOPORELLA RAMULOSA D'Orbigny, 1847 



1847. Monticulipora ramulosa D'Orbigny, Prodrome de Paleontologie Strati- 



graphique, p. 279, no. 1345. 

 1854. Plethopora ramulosa D'Orbigny, Paleontologie frangaise, Terrain Cretace, 



p. 1045, pi. 799. figs. 1-3. 



Structure. — D'Orbigny was deceived by the tuberosities which 

 ornament the zoarial surface and classed this species in Plethopora 

 incorrectly. The section which he illustrated, however, indicates 

 not a single bunch of tubes. We have prepared several excellent 

 longitudinal sections, one of which made from a normal zoarium 

 showed on one side two subcolonies, while on the other side the tubes 

 continued to grow regularly. The enveloping lamella partially sur- 

 rounded the primitive colony and had its origin in a normal tube. 

 All the species with peripheral gemmation pass easily from the free 

 form to the incrusting form and conversely. Another longitudinal 

 section shows that the tubes of the tuberosities are simply somewhat 

 wider than the tubes of the intermediate spaces. The moniliform 

 structure and the gemmation are identical in the two cases. The 

 walls are formed of large vesicles. 



In transverse sections the central tubes are equal in size and 

 polygonal. The smaller ones, which appear sporadically, are indic- 

 ative of the peripheral gemmation. The lozenge-shaped ones of the 

 periphery represent the superior and recurved part of the tubes. 



In tangential sections the tubes are subcircular and buried in a 

 thick vesicular coenenchyma. They are smaller in the intertuberose 

 zones, in conformity with the longitudinal section. The small tubes 

 which appear sporadically are young tubes; they reveal the peripheral 

 gemmation. 



This structure is exactly that of ramose Ceriopora, and it is in this 

 genus that we would have classed this species had we not had the 

 chance to discover the ovicell. The latter is analogous to that of 

 other Cytisidae and is simply more elliptical. 



Occurrence. — Cretaceous (Campanian) : Montmoreau, Brossac, 

 Draullard, St. Aulais, Echebrune and Daviat (Charente), France. 

 Cretaceous (Maastrichtian) : Royan (Charente inferieure), Manie 

 Roux and St. Lheurine (Dordogne), France. 



Plesiotypes. — Canu collection and Cat. No. 68980, U.S.N. M. 



Genus CHARTECYTIS, new genus 



Greek: Chartes, sheet, in allusion to the form of the branches. 



The ovicell is elliptical, transverse, placed in the vicinity of the 

 bifurcations. The tubes are cylindrical, with greatly thickened 

 walls, with regular peripheral gemmation. The orifice is lozenge- 

 shaped, much elongated, without peristome. 



