96 BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 



Occurrence. Midwayan (Clayton limestone) : One mile west of Fort Gaines, 

 Georgia (rare) ; Luverne, Crenshaw County, Alabama (rare). 

 Holotypc.Czi. Xo. 63790, U. S. X. M. 



MEMBRANIPORINA SINESOLUM, new species. 



Plate 19. fig. 5. 



Description. The zoarinm incrnsts oysters; the zooecia are grouped in linear, 

 axial series, emitting laterally zooecia arranged in quincunx. The zooecia are 

 distinct, elongated, elliptical or oval, separated by a deep furrow; the gymnocvst 

 is very small, inconstant, smooth, convex: the mural rim is very thin, flat, slightly 

 enlarged at the base. 



\ko = OAO mm. . (Zs=0.44-0.50 mm 



Measurements. Opesium , Zooecia , - ., 



11,0=0.20 mm. |fe=0.30 mm. 



Affiniti.es. This species has the simplicity of structure of Membraniporina 

 In. en. Eeuss 1869: there is no l>ri*iil i>lt><-i/*t. or. better, it is of extreme tenuity and 

 the substratum is entirely visible. J/. sin-csolum differs, however, in its smaller 

 dimensions (Ao=0.40 mm. and not 0.50 mm.) and in its more regular zooecia. 



This is perhaps Biflnstra lacroiri Smitt. 1S7'2, which was incorrectly deter- 

 mined. However, we are unable to make comparisons, as we have not discovered 

 the recent species or measured the types. 



Membraniporina sinesolum differs from Membranipora capillimnrgo Canu, 

 1911, from the Eocanean of Argentina, in its larger micrometric dimensions 

 (Z,s=0.44-0.50 mm. and not 0.35-0.42 mm.). Menibraniporvna. laxa Reuss 1869, 

 Meinbraniporina c<ti>!lHin<ii'c/o Canu. 1911, Bi-flustro Jacroi.r! Smitt, 1S72 and Mem- 

 lii'iui/jior/iKi xiiirxttJiiij'i. new speris. form a natural group of very great simplicity 

 of structure. Unfortunately we lack recent specimens for study. 



Ocnirn nc< . Lower Jacksonian (Moodys marl) : 2i miles north of Robert, 

 Xewton County, Mississippi (rare). 



Holotype.Cat. Xo. G3876, U. S X. M. 



MEMBRANIPORINA LAXA Reuss. 1869. 



Plate 13 fig. 16. 



1864. Mem'braniiKii-n xniitilimtirgo REUSS. TJeber Anthozoen und Bryozoen des Ma Inzer 

 Tertiarbeckens, Simnifislipriclite fler k. Ak:i(l^inie der \VNseiirliaftfii. AVien, vol. 50. Abth. 1. 

 p. 630. pi. 9. fig. 5. 



1860. Mcmbrniu/inni lu.t-a REUSS, Die fossilen Antbozoeu und Bryozoen der Sehicbteu- 

 Si'uppc von Crosfiro, Denkschriften dor k. Akademie dor Wissoiisi-haften, Wion, vol. 29. Ablli. 

 1. p. 252. pi. 36. fis. 14. 



1904. \li-tiiliriiiniini-ii 1n.ni CANU. Ex]ili>r;ition scientiflqne de la Tunisie, Etude des 

 Bryozoaires tertiaires. p. IT. pi. ?>4, fig. IS. 



Affinities. The figured specimen, which is the only, one collected, is only 

 moderately well preserved, but it presents some interesting peculiarities. There is 

 no dorsal olocyst. the substratum is visible in the opesium. and the calcification is 



