114 BULLETIN 106, INITED STATES NATIONAL MUSEUM. 



rare. They are generally primoserial (fig. 7): their opesium presents a lateral 

 constriction but little accentuated. 



This species is distinguished from the other species of Ilincksina by the absence 

 of visible spines and by its free zoarinm. It is rather common at many localities 

 of the Jacksonian, of which it appears to be a characteristic fossil. 



Occurrence. Middle Jacksonian: Rich Hill. 5-J miles southeast of Knoxville, 

 Crawford County, Georgia (abundant) ; 12 miles southeast of Marshallville, 

 Georgia (abundant); 3 miles north of Grovania. Georgia (abundant): 18 miles 

 west of Wrightsville, Georgia (abundant) ; 17 miles northeast of Hawkinsville, 

 Georgia (abundant) ; near Georgia Kaolin Company Mine, Twiggs County. 

 Georgia (abundant) ; Baldock, Barnwell County, South Carolina (common). 



< '"types. Cut. No. 62573, U.S.X.M. 



HINCKSINA OCALENSIS. new species. 



Plate 22, figs. 10-13. 



Dcsi'rljition. The zoarinm incrusts pebbles and shells. The zooecia are elon- 

 gated, elliptical, and distinct. The mural rim is salient, granulose, convex, very 

 thin at the top, enlarged and crenulated at the base, ornamented with spines of 

 which the distal two are the more constant. The opesium is elliptical, almost entire 

 laterally and crenulated proximallv. The endozooecial ovicell is an indistinct 

 convexity. The ancestrula is an ordinary zooecium, but. smaller and very spinous. 



. \ko=OAO-OA5 mm . \Ls=0.oo mm. 



Mi'dxitreiin-nts. Opesia , . infr Aooecia ' 



[?<9=0.2o-0.27 mm. [fe=0.32-0.3o mm. 



Variations. As always the zooecia are smaller in the vicinity of the ancestrula, 

 so our measurements are invariably taken far from this zooecium. The mural rim is 

 much enlarged (fig. 12), but it always preserves its granular ornamentation and 

 crenulation. As shown in figure 13, perforated zooecia with a large circular aper- 

 ture have been 'noted. 



Affinities. The crenulation of the proximal part of the opesium is very charac- 

 teristic and clearly distinguishes this species from all the preceding ones, and 

 notably from Hincksina jacksonica, with which it might be confounded on account 

 of its micrometric dimensions. 



Hincksina ocalensis is nearest the recent H. madercnsis Waters, 1898. but it has 

 neither the large ovicell nor the five distal spines of that species. 



We have observed this form at numerous localities in the Ocala limestone, and 

 we believe it characteristic of this stage. 



Occurrence. Upper Jacksonian (Ocala limestone) : 7 miles above Bainbridge, 

 Georgia; H miles above Bainbridge, Georgia; near Bainbridge, on the Flint River. 

 Georgia ; Chipola River, east of Marianna, Jackson County, Florida. 



Vicksburgian (Byrammarl) : Byram, Mississippi (identification very doubtful ). 



/ <otyp t g._Cat. Nos. 63879, 63880. U.S.N.M. 



