798 
BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 
Diameter of the peristome 0.12 mm. 
Diameter of the apertura 0.08 mm. 
*.feasui counts. Distance betAveen the peristomes 0.40 mm. 
Separation of the peristomes 0.40 mm. 
Variations. — The peristome is not always salient (figs. 4, 5), which reduces the 
diameter of the apertura (fig. 7). The frontal nervi disappear easily in fossiliza- 
tion (figs. 6, 7). The two large vacuoles adjacent to the apertura are very constant, 
but some others may appear. Generally the more vacuoles there are, the smaller 
they are. The apertures are grouped quite rarely in transversal lines (fig. 9). 
The dorsal face is quite variable. Figure 10 illustrates the most frequent 
occurrence. The nervi become sometimes smaller and more numerous (fig. 11) ; 
rarely they become wider at the expense of the attenuated sulci (fig. 12). 
The tangential section of the frontal always shows three or four vacuoles 
perforating the zoarium (fig-. 13) the structure of which is composed of much 
crowded elements (fig. 14). 
On the dorsal the vacuoles are smaller (fig. 15) and their obliquity is easily 
visible (fig. 16). The removal of the dorsal face by prolonged abrasion shows the 
usual lozenge-shaped interior; the cavity mentioned by Hennig, 1910, therefore, 
does not exist (fig. 17). 
The vacuoles radiate in every direction and are rarely parallel. Many succes- 
sive longitudinal sections are necessary, then, in order to comprehend the zoarial 
structure. Figure 23 shows the great complexity of the dorsal plexus, figure 24, 
the frontal vacuoles; figure 25, the dorsal vacuoles; AA T hile figure 26 illustrates the 
lamellar and squamous structure of the Avails. 
Affinities. — In the number of frontal vacuoles this species is close to Ilornera 
frondiculata Lamouroux, 1821, but it differs from this recent species in its orbicular 
and nonelliptical orifice and in its OAdcell not provided with reticulations. 
It differs from Ilornera striata Milne-Edwards, 1836, in having more than 
tAvo frontal vacuoles and in its dorsal vacuoles being often larger. 
It differs from Ilornera porosa Stoliczka, 1862, in its much smaller dorsal 
vacuoles and in its orbicular and nonelliptical orifice. 
This species is found in all Jacksonian deep-water localities. 
Occurrence. — Middle Jacksonian: Wilmington, North Carolina, (very com- 
mon) ; 31 miles south of Perry, Georgia (common) ; Baldock, Barnwell County, 
South Carolina (rare) ; 18 miles Avest of Wrightsville, Johnson County, Georgia 
(common) ; 12 miles southeast of Marshallville, Georgia (very common) ; 17 miles 
northeast of Hawkinsville, Georgia (common) ; 14 miles southeast of Lilly, Dooly 
County, Georgia (very common); 34 miles north of Grovania, Georgia; one-half 
mile southeast of Georgia Kaolin Co. mine, TAviggs County, Georgia (common). 
Upper Jacksonian (Ocala limestone) : Old factory, about 14 miles above Bain- 
bridge, Georgia (very rare) ; Alachua, Florida (common) ; Avest bank Sepulga 
Iiiver, Escambia County, Alabama (very common). 
Cotypes. — Cat. Nos. 65242, 65312, U.S.N.M. 
