444 
BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 
Occurence. — Middle Jacksonian: Wilmington, North Carolina (rare); near 
Lenuds Ferry, South Carolina (common) ; Eutaw Springs. South Carolina (very 
common) ; Rich Hill, Crawford County, Georgia (common) ; Baldock, Barnwell 
County, South Carolina (common) ; one-half mile southeast of Georgia Kaolin 
Company Mine, Twiggs County. Georgia (common). 
Upper Jacksonian (Ocala limestone) : Alachua, Florida (very rare) ; west 
bank of Sepulga River, Escambia County, Alabama (very rare) . 
Cotypes.— Cat. No, 64118, U.S.N.M. 
METRADOLIUM TRANSVERSUM, new species. 
Plate 57, figs. 1-3. 
Description . — The zoarium is free, bilamellar, erect ; the fronds are foliaceous 
or nearly cylindrical ; the two lamellae, back to back, are inseparable. The zooecia 
are indistinct, elongated, and large; the frontal is convex, thick, and formed of a 
tremocyst resting on an olocyst, with small corresponding pores in quincunx. The 
aperture is elongated, semilunar, with a concave proximal border ; the peristomice is 
oblique, wide, transverse; the rimule-spiramen is wide but little deep; its form 
and its position are irregular. The oral avicularium is small, rare, and inconstant. 
Measurements . — Apertura \ha= 0.20 mm. 
(interior) I?a=0.l7 mm. 
Peristomicef hpe— 0.15 mm. 
(exterior) I lpe=0. 18-0.20 mm. 
Zooecia 
'Lz=0. 80 mm. 
fe=0.40 mm. 
Variations. — On well-preserved specimens the tremopores are placed at the 
bottom of small sulci. These tremopores are small, numerous, regularly arranged 
in quincunx; they are easily altered by fossilization. The peristomice is very 
irregular; the rimule is often placed quite laterally (fig. 2), and it is replaced 
on the proximal border by a salient convexity, which augments still more the trans- 
verse aspect of the peristomice. In old zooecia the rimule disappears, the peri- 
sfomice becomes orbicular and deep ; the species is then unrecognizable. 
Affinities. — This species differs from Metraclolium parvirimulatum in the in- 
constance of its rimule-spiramen, its large micrometric dimensions (Z.s=0.80 and 
not 0.60 mm.), and in the absence of zooecia with spiramen. It differs from 
M etradolium grande in its much smaller rimule, its smaller peristomice (lpe= 0.20 
and not 0.25 mm.), and its more numerous and smaller tremopores. 
It differs from M etradolium sulci ferum in its less deep and more transitory 
sulci, in its very small rimule-spiramen, and the absence of the large oral avicu- 
larium. 
Occurrence. — Middle Jacksonian (Castle Flayne limestone) : Wilmington, 
North Carolina (very common). 
Upper Jacksonian (Ocala limestone) : Chipola River, east of Marianna, Jack- 
son County, Florida, (common). 
Jacksonian (Zeuglodon zone) : Shubuta, Mississippi (very rare). 
Cotypes. — Cat. No. 64120, U.S.N.M. 
