212 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



canal is very small; the opesium of the onychocellarium is longer than the zooecial 

 opesium, oval, the point at the top. 



Measurement*. Opesium of f//0=0.35 mm. 

 zooecium 170=0.25 mm. 



\Lz= 0.45-0.55 mm. 

 Zooecium , 



lZs=0.40-0.45 mm. 



Opesium of (frow=0.45mm. 

 onychocellarium 1 &w=0.17 mm. 



\Lon=Q. 75-0.90 mm. 

 ( Jnycnocellarium 



l?<w=0.30 mm. 



Affinities. This fine species does not exhibit a polypidian convexity, which 

 characteristic clearly distinguishes it from Rectonychocella semiluma; moreover, the 

 prtint of the onychocellarian opesium is more often at the top than at the bottom. In 

 the vicinity of the ancestrula the onychocellaria are much less in width than the 

 zooecia (fig. 6). 



Occurrence. Lower Jacksonian (Moodys marl) : Jackson, Mississippi (com- 

 mon). 



Jacksonian (Zeuglodon zone) : Cocoa Postoffice. Choctaw County, Alabama 

 (rare) ; Shubuta, Mississippi (rare) ; Bluff on south side of Suck Creek. Clarke 

 County, Mississippi (very rare). 



Upper Jacksonian (Ocala limestone), west bank Sepulga Eiver: Escambia 

 County, Alabama (rare) ; Alachua, Florida (rare) ; nine miles north of Ocala, 

 Florida (rare). 



Vicksburgian (Red Bluff clay) : Seven and one-half miles southwest of Bladen 

 Springs, Alabama (rare). 



Cotypes.Czi. Nos. 63967, 63968, U.S.N.M. 



RECTONYCHOCELLA ELLIPTICA, new species. 



Plate 33, figs. 7, S. 



Description. The zoarium incrusts shells (Ostrea) or bryozoa. The zooecia 

 are elongated, hexagonal, distinct, separated by a small furrow or thread. The 

 oryptocyst is concave, deep, finely granulose, and as long as the opesium; the 

 opesium is elliptical, elongated, finely crenulated ; the polypidian convexity is only 

 visible in the vicinity of the ancestrula. The endozooecial ovicell is a barely visible 

 convexity. The onychocellarium is straight, lozenge-shaped, enlarged at the base; 

 its cryptocyst is very small, and its opesium is oval, the point below, with a denticu- 

 lated posterior; the small distal canal often fuses with the cryptocyst of the distal 

 zooecium. The ancestrula is small and exhibits a polypidian convexity. 



(Ao=0.30mm. . [Zs=0.40-0.50mm. 



Measurements QVWA of zooecia 7 Zooecia, .. . 



Uo=0.20mm. lfe=0.34-0.36 mm. 



. f^m=0.34-0.36 mm. 

 Opesia of onvchocellana 



Ifo7i=0.16 mm. 



. f 071=0.60-0.70 mm. 

 Onvchocellaria- , 



I Ion =0.24 mm. 



