158 BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 



The ovicell 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 

 avicula.ria are also interopesial or interzooecial. and they have the same form and 

 arrangement. The rarity of the spines and the partial calcification of the cryptocyst 

 are the only characters of differentiation. 



The recent species belonging to the genus are : 



Amphiblc strum, (Membranipora) ftemingii Busk, 1852. 



Amphiblestrum (Membranipora) trifolium Wood, 1850. 



AmpMblestrum (Membranipora) argentea MacGillivray, 1868. 



Amphiblestmm (Membranipora} nmbonata Busk, 1852. 



The fossil species are: 



AmpMblestrwm (Reptofliistrella) heteropora Gabb and Horn, 1862. 



Amphiblestrum (Membranipora) anterides Brydone, 1910. 



Amphiblestrum harmeri Canu, 1911. 



Amphiblestmm. coriense MacGillivray. 1895. 



AMPHIBLESTRUM HETEROPORA Gabb and Horn, 1862. 



Plate 1, figs. 11-1.3. 



1S62. ReptoflustreUa heteropora GABB arid HORN. 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. ReploflustrelJa Jieteropora ULKICH, Maryland Geological Survey, Eocene, pp. 213-214, 

 pi. 60, figs. S, 9. 



1907. Amiiliiblcstriiiu 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 snbtriansfular, 

 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 example*. 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 rhomboidalform of zooecium: and in the relatively smaller size of the 

 opesium and larger avicularia. Cucullate ooecia. less prominent but otherwise 



