618 
BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 
frontal is formed of a very thick olocyst. The apertura is oval, deeply imbedded 
at the base of a peristomie ; the peristomice is irregular, suborbicular. The deep 
zooecia have a flat frontal, their avicularia are prominent between the super- 
ficial zooecia. The interzooecial avicularia are distinct, elliptical, of the size of 
zooecia; they have a pivot; their orifice is like the beak of a duck; the passage 
of the reflexor muscles of the operculum is indicated by the very small perfora- 
tions on the inferior cavity; the beak is salient above the zoarium. The incom- 
plete zooecia are quite numerous. On many zoaria there are some distinct groups 
of large zooecia and of small zooecia. 
Measurements . — Apertura j A«=0.15 mm. Zooecia f Ls= 0.60 mm. 
(interior) '7a— 0.15 mm. (interior) lfe= 0.30-0.35 mm. 
Variations . — Following the rule, the variations of these Cellepores are quite 
great, but the species is always rather easy to determine by its zoarial size. 
The two primitive lamellae of the Eschara are back to back and their zooecia 
are oriented. It is easy to verify this phenomenon in the longitudinal sections 
(pi. 78, fig. 11), in the transversal section (pi. 78, fig. 15), in the interior (pi. 78, 
fig. 17). The Cellepores are therefore Cheilostomes perfected by the superficial 
budding which does not exist in other families. The exterior zooecia are cumu- 
late but never very much raised. Many zoaria (pi. 78, fig. 11) have some groups 
of large zooecia (pi. 78. fig. 9) perfectly distinct from the groups of smaller, flat 
zooecia (pi. 78, figs. 10, 12, 13). The reason for this dimorphism is absolutely un- 
known to us; to determine it, it would be necessary to examine a very large num- 
ber of specimens as complete and perfect as possible. The total regeneration 
appears to have affected many of the interzooecial avxularia and some small 
frontal avicularia, as in figure 7 of plate 78. 
The tangential sections are very difficult to interpret, but they are very in- 
structive. We there note above all the disorder characteristic of the Celleporidae ; 
no regularity, no symmetry. Figure 1, plate 79, shows a section nearest the sur- 
face; the structure of the frontal walls appears in place or is only manifested by 
the black circles, for the olocyst is very compact; the white marks which surround 
these walls result from the convexity of the zooecia. which are only adjacent at 
their base. Figure 16 of plate 78 shows a deeper section at the level where the 
zooecial walls are adjacent ; the zooecial convexity is raised and the zooecia are 
white. 
Occurence . — Lower Jacksonian (Moodys marl) : Jackson, Mississippi (com- 
mon) ; 2 A miles north of Roberts, Mississippi (common). 
Middle Jacksonian: Wilmington, North Carolina (common); 3A miles south 
of Perry, Georgia (common). 
Jacksonian (Zeugloclon zone) : Cocoa post office, Choctaw County. Alabama 
(very common) ; Pachuta, Clarke County, Mississippi* (very common) ; south side 
of Suck Creek. Clarke County, Mississippi (common). 
