584 BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 



visible exteriorly and placed just in front of the labial mucro; it is hyperstomial, 

 recumbent, somewhat supported on the distal zooecium; it is smooth and formed 

 like the frontal of an olocyst under a pleurocyst. 



SHORT HEXAGONAL ZOOECIA. 



rZs=0.60mm. 



. 

 Zooeda fa=0.4<W>.50 mm. 



LONG ZOOECIA. 



\hft-O.Wmm. . \Lz= 0.64-0.70 mm. 



Apertura , ~ , . /ooecia , A EA cr . 



Vrt=0.14 mm. lis=0.50-0.60 mm. 



Variations. The exterior peristomie is little visible by the illumination from 

 above in our figures; it is more accentuated under the microscope by illumination 

 from below. The young zooecia have a complete peristome (figs. 20, 21) and the 

 areolae are quite visible. On old zooecia the pleurocystal calcification is intense in 

 the vicinity of the areolae, so that the zooecia appear to be surrounded by a wide 

 collar (figs. 18, 19). Sometimes in the interior of the peristomie there are two 

 or three denticles; their fragility is perhaps the cause of their rarity. 



Affinities. The greater affinities of this species are with Pcrigastrella oscifans, 

 and near the ancestrula confusion is possible. Perlgastrella plana differs from it 

 in its greater width (7.3=0.40-0.60 and not 0.30-0.40 mm.) ; in the oval, nonellip- 

 tical form of the zooecia. and in the proximal border of the crenulated apertura. 



Occurrence. Vicksburgian (Marianna limestone) : West bank Conecuh River, 

 Escambia County, Alabama (rare) : Murder Creek, east of Castlebury. Conecuh 

 County, Alabama (common) ; near Claiborne Monroe County, Alabama (very com- 

 mon) ; one mile north of Monroeville, Alabama (very common) ; Salt Mountain, 

 five miles south of Jackson, Alabama (common). 



Vicksburgian (Byram marl) : Byram, Mississippi (rare). 



Cotypes. Cat. Nos. 63918, 64324, U.S.N.M. 



PERIGASTRELLA? COSTIFERA, new species. 



Plate 100, figs. 12-17. 



Description. The zoarium is incrusting cylostome bryozoa. The zooecia are. 

 distinct, elongated, fusiform, provided at their extremity with a long exterior 

 peristomie; the frontal is somewhat convex and bordered laterally with widely 

 spaced areolae ; it is formed of a pleurocyst with interareolar costulcx more or less 

 long. The apertura, invisible exteriorly, appears orbicular and oblique. The 

 peristomice is irregular, oblique, with four distal spines. The ovicell is small, 

 hyperstomial, recumbent, opening into the peristome. 



f/:s=0.35-0.45mm. 



Affinities. On account of its orbicular orifice and its large peristomie. this 

 ies may l>e classed approximately in Lagenipora Hincks, 18SO. Waters, in 1899, 



