Measurements. 



776 BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 



zooecia, the first of which is adjacent to the neighboring fascicles and placed on 

 the median axis. The tubes are small, distinct, separated by a salient thread. The 

 basal lamella is slightly ornamented with convex striations; it is flat or concave 

 and bordered by a more or less wide and thickened margin. 



Diameter of the tubes 0.10 mm. 



Distance between the fascicles 0.20 mm. 



Width of the fascicles 0.10 mm. 



Affl/nitles. This species contains sometimes on the dorsal traces of firmato- 

 pnres. It is very close to Idmonea tacta in its small dimensions and the union of 

 the fascicles on the median crest, but it differs in that the number of tubes is 

 always greater than five. It differs from Idmonea petri D'Archiac. 18-46, in its 

 smaller zoarial dimensions and the much smaller distance (0.20 and not 0.40 mm.) 

 between the fascicles. 



We dedicate this charming and delicate species to Mr. Earle Sloan of Charles- 

 ton, South Carolina, in appreciation of his excellent work upon the geology of 

 his State. 



Occurrence. Middle Jacksonian: Wilmington, North Carolina (very rare); 

 near Lenuds Ferry, South Carolina (common). 



Cotypes. Cat. Nos. 65345, 65480, U.S.N.M. 



IDMONEA MAGNIREVERSA, new species. 



Plate 136, figs. 13-23. 



Description. The zoarium is long, thin, linear, bifurcated, with oval trans- 

 verse section much higher than wlide. The fascicles are salient, close together, 

 adjacent to the median crest, and arranged alternately on each side of it: they 

 contain three or four zooecia. The tubes are visible, convex, with square or orbicu- 

 lar peristome. The dorsal is semicylindrical, very large, much larger and thicker 

 than the frontal, striated longitudinally by the tubes. 



Diameter of the zooecia 0.12 mm. 



Distance between the fascicles 0.20-0.24 mm. 



Width of the fascicles 0.15 mm. 



Width of the zoarium 0.40 mm. 



Variations. The fragments of the zoarium are quite regular in their general 

 aspect, just as is also the number of the zooecia to the fascicles (figs. 15, 16). The 

 only valuation is in the size of the dorsal, which is in rapport with the proximity 

 of the base. The great number of the incomplete zooecia at the extremity of the 

 branches (fig. 16) and the extraordinary development of the dorsal indicates a 

 very long zoarium and of a relatively rather great solidity. 



The longitudinal section (fig. 21) indicates tubes of an extraordinary length. 

 The habitual small pores are rather difficult to see on the tangential sections (fig. 

 20), where the length of the lozenge-shaped spindles confirm the early origin of 

 the tubes and their length (fig. 19). 



Measurements. 



