84 



PROCEEDINGS OF THE NATIONAL MUSEUM 



tiires, short, parietal, sometimes closed by a lamella. The ovicell 

 is orbicular, nonsalient, traversed by 15 tubes. 



Measurements. — Diameter of orifice, 0.09 mm.; diameter of peri- 

 stome, 0.11 mm.; diameter of mesopores, 0.04 mm.; diameter of 

 zoarium, 1.25 mm. 



Structure. — In transverse section the tubes are cylindrical or polyg- 

 onal, with adjacent walls, with regular peripheral gemmation. In 

 longitudinal section the tubes arc long, cylindrical, narrowed at the 

 base, with regular peripheral gemmation in the vicinity of the zoarial 

 axis; they are recurved at their extremity. The mesopores are 

 parietal, but, as their arrangement around the aperture is irregular, 

 they are cut in sections irregularly and present the most varied forms; 



Fig. iZ.—Laterocavea dutempleana D'Orbigny, 1853. A. Meridian section, X 16, through a growing 

 branch, showing the lozenge-shaped areas. B. Longitudinal section, X 16, with an accessory exterior 

 lamella at the left. C. Meridian section, X 16, showing mesopores only in the lateral faces. D. 

 Transverse section, X 16, through a normal branch. E. Longitudinal section, X 16, illustrating the 

 cylindrical tubes with triparietal gemmation around a central tube Lower Cretaceous (Aptian): 

 Faringdon, England 



their walls are very thick. In tangential sections the mesopores are 

 very small and surrounded by very thick calcareous tissues. 



Affinities. — This species differs from Tretocycloecia multiporosa in 

 its much smaller mesopores. It differs from Heteropora Iceepingi 

 Gregory, 1909, which has a similar exterior aspect, in its much smaller 

 zoarium, and in its smaller zooecial diameter (0.09 and not 0.15 mm.) . 



Occurrence. — Lower Cretaceous (Aptian) : Faringdon, England 

 (common) . 



Cotypes.—C&t. No. 69940, U.S.N.M. 



