34 BULLETIN 16 5, UNITED STATES NATIONAL MUSEUM 



Measurements. — 



. (Zs = 0.54 mm. ~ . (Ac = 0.29-0.32 mm. 



Zooecia 7 _ _„ _ „_ Opesium 7 A1 „ nio 



|?,s = 0.27-0.36 mm. L [70 = 0.16-0.18 mm. 



n , . \Lon=0A5 mm. Opesium of|/6O^=0.18mm. 



^ |/(9?i = 0.27mm. onychocellarium|70£>=O.O9mm. 



33 zooecia in 4 sq. mm. 



Structure. — The distal border of the mural rim of the ovicelled 



zooecia is attenuated ; moreover, it is much covered over by the ovi- 



cell; the opercular valve therefore closes the latter in opening and 



remains in a position perpendicular to the zooecial plane. This is 



a frequent case in the Membranipores, especially in Me^nbranipora 



valdemunita Hincks, 1880. 



Occurrence. — Vincentown limesand : Timber Creek and near Mul- 



lica Hill (Gabb and Horn), Vincentown and near Blackwoodstown, 



N.J. (common). Aquia formation (Eocene) : Upper Marlboro, Md. 



(Ulrich and Bassler). 



Plesiotype.— U.S.N.M. No. 52587. 



Family OPESIULIDAE Jullien, 1888 



Genus FLORIDINA Jullien, 1881 



FLORIDINA SUBSCUTATA, new species 



Plate 7, Figure 1 



Description. — The zoarium encrusts shell fragments. The zooecia 

 are distinct, more or less elongated, and sometimes transverse, small, 

 ogival; the mural rim is thin, little salient; the cryptocyst is shal- 

 low, slightly convex, smooth. The opesium is trifoliate, transverse, 

 with proximal border very convex; the opesiular indentations are 

 large and rounded. Onychocellaria present. Ovicell and ancestrula 

 unknown. 



Me asuremen ts . — 



r, . {Lz = 0.4: mm. ~ . (7*0 = 0.11 mm. 

 Zooecia { , _ _ Opesium \ , _ . . 



\h = 0.3 mm. 1 [Io = 0. 14 mm. 



32 zooecia in 4 sq. mm. 



Affinities. — In the genus FToridina, the zooecia have quite variable 

 micrometric dimensions ; not one resembles its neighbor, and certain 

 dimensions vary up to twice the usual size. Those we give are the 

 average taken on the most frequent forms. Our specimen bora only 

 an incomplete onychocellarium. 



The relationships of this species are with Floridina (Meuibrani- 

 pora) scutata Levinsen, 1925, of the Danian of Faxe. We do not 

 identify the two species as the same, because the Danish author did 



