108 BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 



The inner face is but slightly concave : the radial ribs are smooth and perforated 

 with some small scattered pores or ornamented with large tuberosities. 



Measurements. Opesium 



Ao=0.1o mm. . Zz=0.25 mm. 



7 Zooecium , 

 fo=0.12 mm. \ls-0.25 mm. 



Zi>=r0.35 mm. 



Vibraculum , , 



Uv=0.26 mm. 



Variations. The interzooecial sections show that the inner side is very thick and 

 fibrous, and that between the tuberosities there are sometimes very narrow tubules 

 (fig. 9). The tuberosities on the rows of the noncelluliferous face (figs. 10, 12) are 

 not constant (fig. 14), and the same zoarium (fig. 10) shows both smooth and tuber- 

 ous conditions. Gemmation about the ancestrula is not regular. It is linear at first, 

 and the zoarium becomes discoidal by the special budding along lateral lines (fig. 10) . 



In tangential section (figs. 7, 13) the mural rim is seen to be formed of olocystal 

 elements grouped in radial lines around the opesium. A tangential section of the 

 inner face (fig. 6) shows olocystal nuclei corresponding to the tuberosities. The ribs 

 are separated by a white line. 



Affinities. The opesial collar is similar to that described by Levinsen in Mem- 

 branicellaria ; but we have not observed ovicells. 



This species differs from Otionella. perforata in the tuberosities which ornament 

 its noncelluliferous side and in its vibracula, which are larger than the zooecia. 



Occurrence. Claibornian (Cook Mountain formation) : Moseleys Ferry. Cald- 

 well County, Texas (rare). 



Lower Jacksonian (Moodys marl) : Jackson, Mississippi (common). 



Jacksonian (Zeuglodon zone) : South side of Suck Creek, Clarke County, Mis- 

 sissippi (rare). 



Cotypes.Czt. No. 63841, U.S.N.M. 



OTIONELLA CAVA, new species. 



Plato 21, figs. 8-14. 



Description. The zoarium is orbicular. On the outer surface the zooecia are 

 arranged in regular quincunx lines. They are hexagonal, a little elongated, some- 

 what indistinct, confluent through the union of their mural rims ; the mural rim is 

 quite uniformly developed, thick, somewhat enlarged at the base. The opesium is 

 elliptical, elongated, entire. The vibraculum is very large, twice as long as the 

 zooecia, and is interzooecial, unsymmetrical and auriculated; its projecting lip is 

 small. On the inner side the radial ribs are holloiv and not calcified; the zooecial 

 walls are pierced everywhere with small hydrostatic tuberosities. 



Measurements. Opesium 



A0=0.26 mm. . fZs=0.35 mm. 



7 =0.18 mm. eCUlm l7 2 =0.24 mm. 



Z<y=0.65 mm. 



Vibraculum , 



lv=0.'2G mm. 



Affinities. The hydrostatic system of this species is strongly developed and is 

 quite analogous to that of Lunularia (t/'xfifn* Lonsdale, 1845. The external surface 



