246 BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 



1862. Lunulites distans GABB and HORN, Monograph of the Fossil Polyzoa of the Secondary 



and Tertiary formations of North America, Journal Academy Natural Sciences, 



Philadelphia, ser. 2, vol. 5, p. 119. 

 1890. LunuUtes distans DEGREGOEIO, Monographic de la Faune Eocenique de 1'Alabama et 



surtout de celle de Claiborne de 1'Etage parisien, Aunales de Geologie et de 



Paleontologie, Livraisons 7, 8, p. 250, pi. 42, fig. 29. . 

 1858. LunuUtes contigua EMMONS, Geological Survey North Carolina, Paleontology, p. 311, 



figs. 250, 251 '(not L. contigua Lonsdale, 1845). 



Description. The zoarium is a large, convex Lunulites, on which the rows of 

 zooecia alternate with rows of vibracula. The zooecia are disposed in radial and 

 circular rows, and are distinct, elongate, hexagonal, or ogival. The cryptocyst is 

 not distinct from the mural rim ; it is deep, flat, very finely granulated ; more de- 

 veloped in the small than in the large zooecia; the opesium is elongate, ogival, 

 with a slightly concave proximal border. The ovicell reposes on the distal wall; it is 

 a small convexity, distinct from the mural rim. The vibraculum is elongated, narrow, 

 lozenge-shaped, symmetrical, provided with two lateral condyles. The interior of 

 the zoarium is hollow; the zooecia are devoid of basal walls and are wide open 

 into the zoarial cavity. The inner side is a thin calcareous or chitinous pellicule 

 provided in the interior with numerous tuberosities. The ancestrula is a zooecium 

 identical with the others. The ancestrular zooecia are sometimes hydrostatic or 

 radicular. 



Variations. The zoarium generally is of large dimensions (figs. 3, 4, 5). 

 To insure the upright position it is necessary to have an extensive hydrostatic 

 system, because lime is much heavier than the water. This is the reason for the 

 absence of all fibrous tissue. 



This exceedingly light apparatus is very fragile and breaks very easily, for en- 

 tire zoaria are never found. In calcareous sediments the mud fills up the internal 

 cavity and preserves the fragile lamella which covers the zoarium. On these rather 

 common fossils, it may be noted that the inner side (fig. 18) of this lamella bears 

 numerous tuberosities. The radial rows of zooecia are separated by vertical parti- 

 tions supporting the frontal cryptocyst which has been worn away on account of 

 its fragility, although it is easy to reconstruct it in the mind's eye (figs. 1-5). 



The inner side of the zoarium is extremely fragile. Upon the supposition that 

 one of our specimens is a mold of the exterior, an impression of it in wax (fig. 19) 

 gives the external aspect of the inner side, but we have no confirmation of this 

 structure from actual specimens. Quite frequently the zoaria are found with a 

 large cavity representing the place where some incrusting bryozoan or other 

 organism has strengthened the fragile inner side. 



We have found some zooecia with a polypidian convexity (fig. 7) ; the parietal 

 muscles are therefore attached to the cryptocyst. 



The size of the zooecia is quite variable and must depend on the size of the 

 ancestrula and the convexity of the zoarium. Figure 11 illustrates the rare case 

 of a gigantic ancestrula surrounded by large zooecia; generally the zoarium com- 

 mences with radicular zooecia (fig. 8), a zone of small zooecia appears next (figs. 



