522 



BULLETIN 106, UNITED STATES NATIONAL, MUSEUM. 



Affinities. The only specimen found has been figured. It is very pretty, 

 but it has no ovicell. It much resembles Scmihaswellia clara, but is distinguished 

 from it in the place of the spiramen, which is much more distant from the peri- 

 stomice. 



It differs from Tessaradoma grandipora in the much smaller diameter of the 

 peristomice (0.09 and not 0.11 mm.) and in its thin peristome, measuring 0.10 

 and not 0.15 mm. 



FIG. 154. Genus Tessaradoma Norman, 1868. 



A-G. Tessaradoma gracile Sars, 1850. A. Zoarium, natural size. B. Portion of zoariuni, 

 X 20. C. Zooecia, X 60. (After Hincks, 1880.) D. Schematic drawing of a longitudinal sec- 

 tion through the zooecium. E. Drawing showing the introduction of the water by the spiramen 

 in the peristomial tube just at the level of the operculum and above it. (B, D, E after Jullien, 

 1903.) 



a, anter; c, compensatrix ; d, dorsal zooecial wall; f, frontal zooecial wall; gt, tentacular 

 sheath ; mr, retractor muscles of the polypide ; opf, closed operculum ; opo, open operculum ; or, 

 zooecial orifice or aperture ; p, polypide ; pe, peristome ; pis, peristomice ; po, poster ; sp, spira- 

 men ; spm, membraneous portion of the spiramen. 



Occurrence. Middle Jacksonian (Castle Hayne limestone) : Wilmington, 

 North Carolina (very rare). 



Holotype.Cat. No. 6-4170, U.S.N.M. 



TESSARADOMA GRANDIPORA, new species. 

 Plate 67, figs. 2, 3. 



Description. The zoarium is free, compressed, branched, formed of 3 longi- 

 tudinal rows of zooecia ; the dorsal is a tremocyst with sulci bearing a median row 



