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PROCEEDINGS OF THE NATIONAL MUSEUM 



little numerous. There are zonal lines, rather regular, very convex, 

 scattered in the inferior part of the branches and approaching more 

 closely at the summit. The zoarial margins are occupied by epithe- 

 cal lines, very numerous, close together, represented in a drawing 

 with ('iifhculty. The diaphragms are widely spaced and their simul- 

 taneous occurrence forms the zonal lines. The extremity of the 

 tubes is thickened and moniliform; the tubes are not then rigorously 

 cylindrical but show constrictions more and more close to each other. 

 In transverse sections the tubes are polygonal, with thin and 

 adjacent walls. On the edge the epithecal lines are so close together 



Fig. iO.—Leiosoecia constanti D'Orhigny, \S50. A. Longitudinal section, X 16, showing the zonal lines 

 and the undulated tubes with their diaphragms. B. Portion of a transverse section, X I'i, illustrating 

 the polygonal form of the tubes. Lower Cretaceous (Valangian): Sainte-Croi.x, Switzerland 



that they form an exterior epithecal zone so opaque that photog- 

 raphy can show its complexity only imperfectly. 



In tangential section the tubes are little polygonal and the meso- 

 pores are very small. The calcareous tissue which surrounds them 

 is alveolar. 



This species has the same internal structure as Leiosoecia multi- 

 yorosa and Leiosoecia grandipora, but the zonal lines and the epithe- 

 cal lines are more numerous. 



Occurrence. — Lower Cretaceous: Sainte-Croix. Switzerland ^Valan- 

 gian); Grandpre (Anlennes), France (Aptian'). 



Plesiotypes.—C&t. No. 69933, U.S.N.M 



