18 BULLETIN 16 5, UNITED STATES NATIONAL MUSEUM 



Genus MEMBRANIPORIDRA Canu and Bassler, 1917 



MEMBRANIPORIDRA PERAMPLA Gabb and Horn, 1862 



Plate 3, Figures 1, 2 



1862. Membranipora perampla Gabb and Horn, Journ. Acad. Nat. Sci. Phila- 

 delphia, ser. 2, vol. 5, p. 158, pi. 20, fig. 42. 



1907. Membranipora perampla Ulrich and Bassler, in Weller, Geol. Surv. 

 New Jersey, Paleontology, vol. 4, p. 337, pi. 24, fig. 4 (bibliography). 



Description. — The zoarium is encrusting, growing upon other 

 Bryozoa and upon shells. The zooecia are distinct, large, separated 

 by a furrow, hexagonal in outline, arranged in quincunx ; the mural 

 rim is thick, more or less enlarged at the base ; the opesium is wide, 

 elliptical or sometimes nearly circular in outline. The ovicell is 

 hyperstomial, buried in the distal zooecium, convex, smooth. 



Measurements. — 



~ . \ho= 0.47-0.54 mm. „ f Zs- 0.66-0.72 mm.^11 



Opesium { 7 noz? Zooecium ] 7 n .» n „ A '- ' 



r 1^=0.36 ram. | U= 0.47-0.54 mm. 



Variations. — Gabb and Horn found only a single specimen of their 

 species, exhibiting the enlarged cells of undoubtedly a large colony. 

 As similar cells can be frequently observed on the specimens studied 

 by Ulrich and Bassler, it was with good reason that they selected 

 them as representing the species of the older authors. 



As in all the Membranipores, the variations in form and in dimen- 

 sions are very great. The proximal portion of the mural rim, becom- 

 ing much enlarged, is transformed into a true cryptocyst and gives 

 to the cells a very different aspect, but precisely that figured by 

 Gabb and Horn. 



In appearance the ovicell seems to be endozooecial, but with dis- 

 section the distal portion of the mural rim is visible although 

 attenuated, and the ovicell cicatrix surmounts it regularly. This 

 is the characteristic of Membraniporidra in which the hyperstomial 

 ovicell is closed by the operculum. On the fossils the distinction 

 between the two kinds of ovicells is often difficult to observe. Here 

 in inclining the preparation one sees clearly under the ovicell the 

 transverse slit through which the ovicelled cavity communicated 

 with the cell. Regenerated zooecia are not rare. 



Occurrence. — Vincentown limesand : Very common at Vincentown 

 but rare near Blackwoodstown, N.J. 



Plesiotypes.— U.S.N.M. Nos. 52603, 73865. 



ELLISINIDRA, new genus 



The ovicell is hyperstomial and closed by the operculum. An 

 interzooecial avicularium, small, transverse, dependent, occurs above 

 each zooecium. Dietellae are present. 



