578 
BULLETIN 106, UNITED STATES NATIONAL MUSEUM, 
rocyst. The apertura is hidden at the base of a large peristomie ; it is transverse 
(interior) and formed of a semielliptical anter separated by two small cardelles 
from a somewhat concave poster; the peristome is very salient, thin; its distal 
part supports eight spines; its proximal part bears a wide, very salient mucro per- 
pendicular to the zooecial plane or depressed on the frontal. The ovicell is small, 
salient, globular, smooth ; it is hyperstomial and recumbent. 
Measurements. — Apertura 
| ha= 0.12 mm. 
U<z= 0.14=0. 18 mm. 
Zooecia 
f Z.3= 0.80-1.00 mm. 
I Zs=0.70-0.80 mm. 
Affinities . — This large and beautiful species has been known for a long time. 
The transversal schematic section of a zooecium given by Gabb and Horn is per- 
fectly exact. The labial mucro is placed in such a position that our photographs 
can not show their important saliency. 
The operculum may never close the ovicell. 
This species differs from Perigastrella semierecta Koschinsky, 1885, in its 
larger dimensions (Lz= 0.80 and not 0.70 mm.) and the different disposition of 
the labial mucro. 
Occurrence. — Middle Jacksonian: Wilmington, North Carolina (common); 
near Lenuds Ferry, South Carolina (very rare). 
Upper Jacksonian (Ocala limestone) : West bank Sepulga Eiver, Escambia 
Countjq Alabama (rare). 
Plesiotypes. — Cat. No. 61195, IT.S.N.M. 
PERIGASTRELLA OSCITANS, new species. 
Plate 72, figs. 15-18. 
Description . — The zoarium incrusts shells, often over a very large surface. 
The zooecia are distinct, elongated, elliptical; the frontal is convex and surrounded 
by a line of round or triangular areolae; it is formed of a granular pleurocvst. 
The apertura (interior) is oblique, transverse, trapezoid; the peristomie, rather 
deep, often bears two or three very prominent denticles; the peristome is thin, 
salient, complete; it bears six spines on its distal part and the proximal part is 
a wide salient mucro, erect, and partially hiding the apertura. The ovicell is 
small, transverse, salient, very widely open; its pleurocyst does not entirely cover 
the olocyst, thus leaving a very apparent frontal area. 
Measurements. — Apertura 
|7m,= 0.08 mm. 
|?a=0. 08-0.10 mm. 
Zooecia 
Z3=0.60-0.70 mm 
72=0.30-0.40 mm. 
Valuations. — It is difficult to find good specimens of this species, for they are 
easily altered by fossilization ; the apertura is always more or less closed bv the 
calcareous deposit. We have succeeded, however, in preparing a superb specimen 
(fig. 15) in the vicinity of the ancestrula; the areolae are there quite small and the 
labial mucro is much attenuated. The more habitual aspect of the species is that 
of our figure 16. 
