158 
BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 
The ovieell is widely open above the operculum. It is formed of two calcareous 
lamellae, the upper of which being incomplete, limits the frontal area or callosity 
as in the genus Callopora Gray, 1848. But we insist it is also entirely covered 
by the membranous ectocyst, quite as in all the other Cheilostomata. 
The relations of this genus with Callopora are very great. In the latter the 
avicularia are also interopesial or interzooecial. and they have the same form and 
arrangement. The rarity of the spines and the partial calcification of the crvptocyst 
are the only characters of differentiation. 
The recent species belonging to the genus are: 
Amp hible strum ( Membranipora ) flemingii Busk, 1852. 
Amphiblestrum {Membranipora) trifolium Wood, 1850. 
Amphiblestrum (M embranipora') argentea MacGillivray, 1868. 
Amphiblestmm ( Membranipora ) umbonata Busk, 1852. 
The fossil species are: 
Amphiblestrum ( Reptoflustrella ) heteropora Gabb and Horn, 1862. 
Amphiblestrum' {M embranipora) anterides Brydone, 1910. 
Amphiblestrum harmeri Canu, 1911. 
Amphiblestrum coriense MacGillivray, 1895. 
AMPHIBLESTRUM HETEROPORA Gabb and Horn, 1862. 
Plate 1, figs. 11-13. 
1S62. Reptoflustrella heteropora Gabb and Hobn, Monograph of the Fossil Polyzoa of tue 
Secondary and Tertiary formations of North America, Journal of the Academy of 
Natural Sciences of Philadelphia, ser. 2, vol. 5, p. 12, pi. 20, fig. 50. 
1901. Reptoflustrella heteropora Ulrich, Maryland Geological Survey, Eocene, pp. 213-214, 
pi. 60, figs. 8, 9. 
1907. Amphiblestrum heteropora Weller, Geological Survey of New Jersey, Paleontology, 
vol. 4, p. 333, pi. 23, figs. 14-16. 
Description. — Colony incrusting in irregular patches. Cellules in a single 
layer, placed with but little regularity, but with a tendency to radiating lines; 
elongate, acuminate anteriorly, broadly truncate behind. Opening subtri angular, 
with the sides convex, often approaching an oval in very long cellules. Surface 
regularly convex, bordered anteriorly and laterally by a slightly elevated, rounded 
edge, usually becoming obsolete as it approaches the proximal end of the cellule. 
Special pore placed in advance of the opening, small and round. No ovarian 
vesicles were observed. Old cellules are closed over by a continuation of the surface 
wall totally obliterating the aperture. In this case the “ special pore ” is also gen- 
erally obliterated, merely showing a slight depression. (Gabb and Horn, 1862.) 
The Eocene specimens are coarser in appearance than the Cretaceous form 
of the species, of which the writer has a number of excellent examples. They differ 
further in the more pronounced character of the granulation of the front wall and 
opesial margin, the Cretaceous form being almost smooth; in more frequently 
assuming a rhomboidal form of zooecium ; and in the relatively smaller size of the 
opesium and larger avicularia. Cucullate ooecia, less prominent but otherwise 
