NORTH AMERICAN EARLY TERTIARY BRYOZOA. 



213 



Variations. The specimens from Jackson. Mississippi, have the zooecia very 

 distinctly marked, because they are separated by a thin and salient thread, which 

 gives them a particular aspect very difficult to define. In the other localities the 

 zooecia are united among themselves and quite indistinct, giving these specimens a 

 very different appearance. Nevertheless, the other characters are identical. 



The onychocellarian opesium is a little longer than that of the zooecium, 

 but the character is not evident at first glance because of its slight width. 



The fusion of the distant canal of the onychoccllarium with the cryptocyst of 

 the distal zooecium is not general 

 and the extreme point of this organ 

 is often distinct without ever being 

 prominent. 



Affinities. The difference be- 

 tween this species and Rectonycho- 

 ceUa bilamellaria is almost entirely 

 zoarial. Still, there are some slight 

 zooecial differences; the opesium is 

 elliptical, without an enlarged, 

 straight or convex proximal border, 

 and the length of the onychocel- 

 larian opesium is a little greater than 

 the opesium of the zooecium. 



The species differs from Rec- 



tonychocella tennis in its smaller mi- A _ D Vdumdla (0nyehoc clU) Uvinscni Canu and 



Bassler, 1917. A. A group of zooecia, the two upper- 

 most with ovicell, X 40. B. A zooecium with 

 ovicell(ou). In the covering membrane of the aper- 

 ture is seen a simple chitinized operculum, and in 

 each of the two sinuses of the aperture is the end of 

 a parietal muscle, X 55. C. A zooecial operculum 

 above which there is an ooecial operculum, X 75. 

 D. Avicularian mandible, X 40. 



FIG. 58. Genus Vdumdla Canu and Bassler, 1917. 



crometric dimensions (Lz=0.45 mm. 

 instead of 0.55 mm.) and in its ony- 

 chocellarian opesium which is smaller 

 and more tapering below. 



Occurrence. Upper Jacksonian 

 (Ocala limestone) : Bainbridge, Geor- 

 gia (rare) ; Chipola River east of 

 Marianna, Florida (rare) ; West 

 Bank Sepulga River, Escambia County, Alabama (rare). 



Coupes. Cat. Nos. 63969, 133970, U.S.N.M. 



Genus VELUMELLA, Canu and Bassler, 1917. 



1917. Vdumdla CANU and BASSLER, Synopsis of American Early Tertia-ry Cheilostome 

 Bryozon, Bulletin 96, United States National Museum, p. 26. 



The retractor muscles of the polypide are attached in the medion axis of the 

 zooecium; the opesiular indentations are symmetrical. The onychocellaria are 

 straight, without distal canal; the rachis of the mandible bears two broad mem- 

 branes; the opesium of the onychocellarium is elliptical and entirely denticulated. 



