732 BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 



The zoarium is never exactly cylindrical and claviform fronds are not rare. 

 The zoarial base is a little hook and not a calcareous basal expansion. 



Affinities. This species differs from Mecynoecia lunata in its thinner branches 

 with 8 rows of tubes instead of 12, and in its smaller peristome (0.12 and not 

 0.1G mm.). It differs from Mecynoecia elongatotiiba in 8 rows of tubes instead 

 of 6, and in its generally much smaller distance between the peristomes (0.90 and 

 not 1.20 mm.), and from Entalophora pulcheUa Reuss, 1847. in its longer peristomie. 



Occurrence. Vicksburgian (Marianna limestone) : West bank of Conecuh 

 River, Escambia County, Alabama (very common) : Salt Mountain, 5 miles south 

 of Jackson, Alabama (rare) ; Murder Creek, east of Castlebury, Conecuh County, 

 Alabama (rare) ; deep well, Escambia County, Alabama (rare) ; 1 mile north of 

 Monroeville, Alabama (very common). 



Vicksburgian (Red Bluff clay) : One-fourth of a mile of Woodwards, Wayne 

 County, Mississippi (rare). 



Cotypes.^Cnt. Nos. 15394, 65395, U.S.N.M. 



MECYNOECIA ELONG ATOTUBA, new species. 



Plate 155, figs. 23-29. 



Description. The zoarium is a cylindrical and bifurcated Entalophora with 

 six longitudinal rows of zooecia. The tubes are distinct, convex, very long, striated 

 transversally, bent upward at their extremity and terminated by a short very 

 oblique peristomie; the peristome is thin, orbicular, oblique. 



Diameter of peristome 0.12 mm. 



Measurem en ts. 



Distance between the peristomes 0.90-1.20 mm. 



Separation of the peristomes 0.44-0.50 mm. 



Diameter of the branches 0.90 mm. 



Variations. The length of the tubes is very characteristic but it is not con- 

 stant; on certain branches it is only 0.80 mm.; it is never more than 1.20 mm. The 

 branches are never exactly cylindrical : their base is often narrowed. 



The ovicell and the base are unknown. 



Affinities. This species differs from Mecynoecia semota, of which the diame- 

 ter of the peristome is identical in its thinner branches with six rows of zooecia 

 instead of eight and in the long distance between the peristomes almost always 

 greater than 0.90 mm. 



It differs from Mecynoecia parvituba, of which it has a little the general 

 aspect, in its larger peristomial diameter (0.12 and never 0.10 mm.). 



Occurrence. Vicksburgian (Red Bluff clay) : Seven and one-half miles south- 

 west of Bladen Springs, Alabama (common). 



Vicksburgian (Marianna limestone) : Murder Creek, east of Castlebury, 

 Conecuh County, Alabama (very rare). 



C otypes. Cat. No. 65463. U.S.N.M. 



