AMERICAN EARLY TERTIARY BRYOZOA. 159 



similar to those of Membranipora spiculosa, occur not infrequently upon the Cre- 

 taceous specimens but are wanting on the Eocene material in hand. When these 

 occur they take the place of the avicularium which otherwise occurs invariably on, 

 or just above, the upper rim of the zooecium. (Ulrich. 1901.) 



Occurrence. Cretaceous (Vincentown) : Mullica Hill and Vincentown, New 

 Jersey (common). 



Lowest Eocene (Bryozoan bed at base of Aquia formation) : Upper Marlboro, 

 Maryland (rare). 



AMPHIBLESTRUM PRODUCTUM, new species. 



Plate 4, figs. 2, 3. 



Description. The zoarium incrusts rocks and shells. The zooecia are small, 

 very elongated, distinct, often with a small gymnocyst: the mural rim is salient, 

 being enlarged below into a concave cryptocyst nearly as long as the opesium. The 

 opesium is small, anterior, elliptical, entire. The hyperstomial ovicell, never closed 

 by the operculum, is elongated, very salient, and has a frontal carina. The avicu- 

 laria are narrow, long, fusiform, pointed, and slightly projecting at the top, 

 without pivot, 



nr /-. |Ao=0.15 mm. . fZs=0.35 mm 



Measurements. Opesia Zooecia 



1/0=0.10-0.12 mm. 1/2=0.20-0.25 mm. 



Avicularia Zav=0.20-0.25 mm. 



Variations, affiniti/-*. The length of the avicularia is very variable: they are 

 frequently primoserial; their mandible must be triangular. The ovicell has no 

 callosity, but is ornamented with a longitudinal keel. Thi> change in ornament 

 has no generic importance. 



The zooecia have a little resemblance to Amphiblestrum wirvatum, but the 

 present species differs from the latter in its straight avicularia. 



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

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



Cotypes.G&t. Nos. 63796, 63797, U.S.N.M. 



AMPHIBLESTRUM BIPOROSUM, new species. 



Plate 29, figs. 13, 14. 



The zoarium incrusts shells. The zooecia are small, wide, pyriform, and dis- 

 tinct : the cryptocyst is concave and as long as the opesium. The opesium is ante- 

 rior, somewhat trifoliate. The ovicell is hyperstomial and never closed by the 

 operculum. Below each zooecium there are two small simple avicularia, slio-htly 

 projecting, round or elliptical, irregularly placed, leaving two pores on the fossils. 



lf . \/io=0.l5 mm. (Zs=0.3G-0.32 mm. 



Measurements. Opesia' An Zooecia , ... 



\lo=O.W mm. |?0=0.25 mm. 



Affinities. The cryptocyst is formed simply by the pro^i-c^ive enlargement 

 of the mural rim. This species has the aspect of DacryoneU'i o< ^onarium but differs 



