66 



PROCEEDINGS OF THE NATIONAL MUSEUM 



Measurements. — ■Diameter of orifice, 0.08 mm.; diameter of 

 branches, 2.5 mm.; length of orifice, 016-0.20 mm. 



Structure. — In transverse section the tubes are cylindrical, with 

 greatly thickened walls; the central tube is perhaps a little larger. 

 In longitudinal section the tubes are very long, with peripheral gem- 

 mation, very regular, with thickened walls. 



This structure is quite simple. In general these forms of the 

 tubes are oriented on one zoarial side; here the colony has two 

 cellular sides, a rare occurrence. 



Occurrence. — Lower Cretaceous. Valangian at 

 Sainte-Croix, Switzerland; Hauterivian at Censeau 

 (Doubs) ; Neocomian at St. Claude and Cinquetral 

 (Doubs), France. 



Coty pes. —Cd,t. No. 69904, U.S.N. M. 



Genus RETENOA Gregory, 1909 



1909. Retenoa Gregory, Catalogue of Cretaceous Bryozoa 

 in the British Museum, vol. 2, p. 28. 



Cytisidae, with an erect frondose zoarium, com- 

 posed of a network of dichotomous, anastomosing 

 branches. The apertures all open on one face of 

 the zoarium. The tubes are cylindrical, with loz- 

 enge-shaped orifices, with intrazoarial gemmation. 



Genotype. — Retenoa (Frondipora) campicheana 

 D'Orbigny, 1853. 



This genus is little different from Homoeosolen 

 Lonsdale, 1850. It differs exteriorily in the absence 

 of pinnules, and especially in its reticulate zoarium, 

 which is a character of little importance. However, 

 the gemmation is intrazoarial and not dorsal, which 

 is a genuine difference. Gregory erroneously in 1909 

 classified this genus in the family Theonoidae; it is 

 one of the typical Cytisidae on account of the nature 

 of its ovicell. 



RETENOA CAMPICHEANA D'Orbigny, 1853 



Plate 7, figs. 5-7 



1853. Frondipora campicheana D'Orbigny, Pal6ontologie frangaise, Terrain 



Cr^tace, vol. 5, p. 678, pi. 783, figs. 12-16. 

 1909. Retenoa campicheana Gregory, Catalogue of the Cretaceous Bryozoa in the 



British Museum, vol. 2, p. 28. (Geologic distribution.) 



Structure. — We have had the good fortune to discover numerous 

 ovicelled specimens. The ovicell is an elliptical capsule, limited, 

 convex, smooth, placed laterally on the dorsal, usually beneath the 

 bifurcations. 



Fig. '29,.—Reienoa cam- 

 picheana D'Orbigny, 

 1853. Longitudinal 



■ section, X 16, showing 

 the cylindrical tubes 

 and the intrazoarial 

 gemination. Lower 

 Cretaceous (Valan- 

 gian): Sainte-Croix, 

 Switzerland 



