114 
BULLETIN 106, UNITED 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 zoarium. It is rather common at many localities 
of the Jacksonian, of which it appears to be a characteristic fossil. 
Occurrence. — Middle Jacksonian: Rich Hill. 51 miles southeast of Knoxville, 
Crawford County, Georgia (abundant) ; 12 miles southeast of Marshallville, 
Georgia (abundant) ; 3J 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). 
Cotypes. — Cat. No. 62573, U.S.N.M. 
HINCKSINA OCALENSIS, new species. 
Plate 22, figs. 10-18. 
Description. — The zoarium 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 proximally. The endozooecial ovicell is an indistinct 
convexity. The ancestrula is an ordinary zooecium, but smaller and very spinous. 
1/ easurements . — Opesia 
[ ho =0.40-0.45 mm 
|?u=0.25-0.27 mm. 
Zooecia 
Lz— 0.55 mm. 
fe=0.32-0.35 mm. 
V ariations.— 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 Ilincksina jacksonica , with which it might be confounded on account 
of its micrometric dimensions. 
Hincksina ocalensis is nearest the recent 11. maderensis 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 ; 14 miles above Bainbridge, Georgia ; near Bainbridge, on the Flint River, 
Georgia; Chipola River, east of Marianna, Jackson County, Florida. 
Vicksburgian (Byram marl) : Byram, Mississippi (identification very doubtful). 
Cotypes. — Cat. Nos. 63879, 63880, U.S.N.M. 
