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 peristomlce 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. Aperttirajfoi=0.15 mm. Zooecia fZs=0.60 mm. 



(interior) 'Za=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. 14). 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 av : cularia 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. 



Occurrence. Lower Jacksonian (Moodys marl) : Jackson, Mississippi (com- 

 mon) ; 2^ miles north of Roberts, Mississippi (common). 



Middle Jacksonian: Wilmington, North Carolina (common): 3i miles south 

 of Perry, Georgia (common). 



Jacksonian (Zeuglodon zone) : Cocoa post office, Choctaw County. Alabama 

 (very common) ; Pachuta, Clarke County, Mississippi (very common) ; south side 

 of Suck Creek, Clarke County, Mississippi (common). 



