376 BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 



anter separated by two large cardelles from a convex rather large poster; it is 

 surrounded by an incomplete peristome bearing 6 large spines. The ovicell is 

 prominent, globular, smooth; it opens above the aperture. The avicularian zooecia 

 are provided with a long, thin beak rounded at the extremity. 



fAfl=0.10mm. . fZs=0.40mm. 



Measurements. Aperturei, n nfr /ooecia< 7 A nc _ an 



lZa=0.07mm. [Iz=Q.25-O.SO mm. 



Affinities. The avicularian zooecia are very interesting; the beak develops 

 around the aperture which does not preserve its form. The extensor muscle of 

 the mandible passes by a sort of very narrow rimule (fig. 19) or by a wider one 

 (fig. 18). 



Such transformations exist in the Celleporidae. Waters noted very similar 

 avicularian zooecia in Holoporella pigmcntaria Waters, 1909. 1 



Another interesting peculiarity is the complete absence of dorsal olocyst. easy 

 to see on the broken zooecia of figure 19. This economy of calcification is rather 

 frequent on the incrusting species. This new species differs from Hippoporina 

 lucens and Hippoporina porcellan-a Busk, 1860 (=Lepralia cleidostoma Smitt, 

 1872), in the presence of avicularian zooecia and the absence of frontal avicularia. 



Cotypes.Cat. No. 63824, U.S.N.M. 



Occurrence. Midwayan (Clayton limestone) : One mile west of Fort Gaines, 

 Georgia (rare). 



HIPPOPORINA LUCENS, new species. 



Plate 48, figs. 15-17. 



Description. The zoarium incrusts shells. The zooecia are small, distinct, 

 ovoid; the frontal is smooth, convex, polished. The aperture is elongated; the 

 almost circular anter is separated by two large cardelles from a poster rather wide 

 and straight. The ovicell is globular, salient, smooth; it is hyperstomial and opens 

 above the aperture by an arched crescent shaped slit. The avicularium is very 

 salient; its mandible is nearly perpendicular to the zooecial plane: it has a cal- 

 careous pivot. 



JAa=0.10-0.12 mm. . fZs=0.36-0.40mm. 



Measurements. Aperture i, n nn _ ., Zooecia, 



Ua=0.09-0.10 mm. jfe=0.20-0.2J: mm. 



Variations. The avicularium is very inconstant; it does not exist on all 

 zooecia; its rupture causes the formation of an irregular cavity (fig. 15). The 

 ovicell is formed of two calcareous lamellae perfectly distinct when broken (fig. 

 17). The frontal also becomes covered with a more or less granulated calcareous 

 deposit (figs. 15, 16) of the origin of which we are ignorant. 



Affinities. This species is very close to Hippoporina cleidostoma Smitt, 1872 

 (=H. porcettana, Busk, 1860), which is still living in the regions of Madeira and 

 Florida. It differs from it in the position and form of its avicularium and the 

 much smaller width of its aperture (0.09-0.10 mm. instead of 0.10-0.13 mm. men- 



1 Reports on the Marine Biology of the Sudanese Red Sea, XII, Journal I.innean Society, vol. 31, p. 16H, 

 pi. 17, flg. 22. 



