30 BULLETIN 16 5, UNITED STATES NATIONAL MUSEUM 



1929 (Eocene, Miocene), and Collarina Jullien, 1888 (Eocene). The 

 simple pores have here become complete and very active avicularia. 



It is impossible to obtain a transparent thin section of this 

 species, as the calcareous elements in it are absolutely opaque. In 

 transverse sections the median lamella is simple and the two zoarial 

 lamellae are inseparable. 



Occurrence. — Vincentown limesand: Vincentown, N. J. (not com- 

 mon). 



Hole-type and plesiotype. — U.S.N.M. No. 52661. 



CALLOPORA NOXONTOWNENSIS, new species 



Plate 6, Figures 5, 6 



Description. — The zoarium encrusts fragments of shells. The 

 zooecia are distinct, separated by a deep furrow, elongated, oval, 

 with a proximal gymnocyst covered by 1 or 2 avicularia; the mural 

 rim is thick, enlarged at the base, decorated with 4 hollow apertural 

 spines and granular. The opesium is oval, finely crenulated. The 

 ovicell is hyperstomial, not closed by the operculum, globular, 

 smooth. The avicularia are triangular, unoriented, oblique on the 

 zooecial plane; the beak is pointed, very salient. 



Measurements. — 



„ . (Zs = 0.5-0.55 mm. ~. . \ho = 0.27 mm. 

 Zooecia \ , n „ r _. _,_ Opesium { 7 _ in n 1 K 



lfe = 0.25-0.27 mm. L \lo = 0.12-0.15 mm. 



28 zooecia in 4 sq. mm. 



Variations. — When the zooecia are not ovicelled there is generally 

 but a single avicularium. It develops into two small avicularia above 

 the ovicell. 



The special characteristic of this species lies in its 4 hollow spines. 

 The 2 distal spines are not placed on the mural rim but are always 

 adjacent to it; the other 2 are on the mural rim but a little lower 

 down, probably in the neighborhood of the articulation of the 

 opercular valve; on the fertile zooecia they are adjacent to the ovi- 

 cell ; often one of them appears lacking, but on the fossils these small 

 details disappear easily. 



Occurrence. — Vincentown limesand : Noxontown Millpond, Del. 

 (very rare). 



Holotype.—TJ.S.'NM. No. 73882. 



Genus AMPHIBLESTRUM Gray, 1848 



AMPHIBLESTRUM (?) ABORTIVUM Gabb and Horn, 1862 



Plate 7, Figures 2-8 



1862. Flustrella capistrata Gabb and Horn, Journ. Acad. Nat. Sci. Philadelphia, 

 ser. 2, vol. 5, p. 161, pi. 20, fig. 48. 



