46 PROCEEDINGS OP THE NATIONAL, MUSEUM vol. 67 



salient thread, a phenomenon produced in many other species with 

 tubes much longer. Finally, there is never an operculum, and the 

 ovicell is very different from that in the Eleidae. The separating 

 threads outline the peristome entirely, a characteristic which deceived 

 D'Orbigny. 



Structure. — In longitudinal section the tubes are short, cylindrical^ 

 somewhat expanded nevertheless in the vicinity of the pseudofacettes; 

 gemmation is triparietal on a basal lamella. 



The transverse section does not show a large number of tubes ; they 

 are polygonal, with thin and adjacent walls ; the smallest are in the 

 vicinity of the median lamella. 



Occurrence. — Lower Cretaceous: Sainte-Croix (Vaud), Switzerland 

 (Valangian) ; Morteau (Doubs), France (D'Orbigny) (Neocomian). 



Plesiotypes.—Csit. No. 69894, U.S.N.M. 



NEMATIFERA ACUTA D'Orbigny, 1853 



Plate 4, fig. 12 



1853. Bidiastopora acuta D'Orbigny, Pal^ontologie francaise, Terrain Cr^tace, 

 vol. 5, p. 799, pi. 784, figs. 3-5. 



Measurements. — Diameter of orifice, O.OS-0. 10 mm.; diameter of 

 peristome, 0.12 mm.; diameter of zooecium, 0.20 mm. 



This species is well characterized by its very thin and sharp zoa- 

 rial margins. The separating threads turn around the peristome, 

 which is thin; the pseudofacettes are flat. 



We have not had the chance to discover the ovicell, and we have 

 classified the species according to its exterior analogies and the trans- 

 verse section which is always easily observed. 



According to Pergens, 1889, Bidiastopora campicJieana D'Orbigny, 

 1853, is a synonym, but we do not believe this is true; moreover 

 D'Orbigny's figure indicates an altered specimen. 



Marsson, 1887, believed he had found this species in the Cam- 

 panian of Riigen. We have not rediscovered it ourselves. 



Occurrence. — Lower Cretaceous (Valangian) : Sainte-Croix (Vaud) , 

 Switzerland. 



Plesiotype.—Csit. No. 69895, U.S.N.M. 



NEMATIFERA INCRUSTANS. new species 



Plate 4, figs. 5-7 



Description. — The zoarium encrusts shells, with many irregularly 

 arranged lamellae ; it emits free, thick expansions irregular around a 

 median lamella. The tubes are distinct, separated by a salient thread, 

 flat, short (pseudofacettes). The peristomes are orbicular, salient. 



