NORTH AMERICAN EARLY TERTIARY BRYOZOA. 731 



Measurements. 



Diameter of the peristome 0.140.10 mm. 



Diameter of the apevtura 0.08 mm. 



Distance between the peristomes 0.70 mm. 



Separation of the peristomes 0.50 mm. 



Diameter of the branches 1.00 mm. 



Variations. The young zooecia are convex and are not bordered by a salient 

 thread. The peristomie. is not constant and is never very salient. The peristomes 

 are often grouped in obliqife verticells, an arrangement which characterizes the 

 form Peripora of D'Orbigny. 



Affinities. This species differs from Mecynoecia cylindrica in its larger peris- 

 tome (0.16 and not 0.10 mm.). It differs from Mecynoecia quh<'-nl>crryae in the 

 absence of overlapping wrinkles and in its smaller peristome (0.16 and not 0.20 

 mm.), and from Mecynoecia semota in the lesser distance between the peristomes. 

 in the less salient peristomies, and in its never claviform zoarium. 



The immense oeciostome characterizes this species very well. 



Occurrence. Vicksburgian (Marianna limestone) : West bank C'onecuh River, 

 Escambia County, Alabama (very common) ; near Claiborne, Monroe County, 

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

 (very common). 



Ootypcs.Cnt. No. 65391-65393, U.S.N.M. 



MECYNOECIA SEMOTA, new species. 

 Plate 15G, figs. 9-25. 



Description. The zoarium is a cylindrical or claviform Entalophora never 

 containing more than eight longitudinal rows of zooecia. The tubes are horn- 

 shaped, narrowed at the back, enlarged in the vicinity of the peristome, distinct, 

 convex, striated transversally, bent upward at their extremity and terminated by 

 a free peristomie; very oblique and salient; their peristomes are widely separated 

 from each other, orbicular or elliptical. The ovicell is in elongate and symmetrical 

 sack. 



Diameter of the salient peristome 0.12 mm. 



Diameter at the base of the peristomie 0.16 mm. 



Distance between the peristomes 0.90 mm. 



Separation of the peristomes 0.60 mm. 



Length of the peristomie 0.31 mm. 



Diameter of the zoarium 1.00 mm. 



Variations. The micrometric dimensions of this species are quite variable and 

 one should not attempt to determine isolated specimens. Our measurements (ex- 

 cept the first) are only the most frequent averages. On certain specimens the dis- 

 tance is only 0.50 mm. and abruptly on others it attains 1.00 mm.; in the latter 

 case its distinction from Mecynoecia elongatotuba is very slight. The separation 

 of the peristomes is a little less variable; it varies, however, between 0.50 and 

 0.60 mm. 



Measurements. 



