NORTH AMERICAN EARLY TERTIARY BRYOZOA. 131 



genus Valdemunitella. The form of the large interzooecial avicularia, the absence 

 of the pivot, and the peculiar form of the mandibles are important arguments for 

 the differentiation and the creation of a separate genus, but this is a study for 

 the future. 



GRAMMELLA CRASSIMARGINATA Hincks, 1880. 



Plate 24, figs. 13-15. 



1880. jUcmbranipora crassiihanjinata HINCKS. General History of the Marine Polyzoa, I 

 Madeiran Polyzoa, Annals Magazine Natural History, ser. 5, vol. 6, p. 71, pi. 9, fig. 1. 



1891. Mcinl>runiitra crnsnininrfiiiKitu HTXCKS. General History of the Marine Polyzoa, 

 Appendix, Annals and Magazine Natural History, ser. 6, vol. S, p. 86. 



1898. Membranipora crassimarginata WATERS, Observations on Membraniporidae, Jour- 

 nal Linnean Society London, Zoology, vol. 26, p. 685, pi. 47, fig. 4. 



1900. CrassimarginatcUa crassimarginata CANTJ, Revision des Bryozoaires du cretace figures 

 par d'Orbigny, Pt. 2, Cheilostomata, Bulletin Society Geologique de France, vol. 

 28. p. 369. 



1903. OocJiilina crassimarginata NORMAN, Notes on the Natural History of East Finniark. 

 Polyzoa, Annals and Magazine Natural History, ser. 7, vol. 11, p. 595. 



1909. Hembranipora crassimarginata NORMAN, The Polyzoa of Madeira and neighboring 

 Islands, Journal Linnean Society London, vol. 30, p. 287. 



1860. Alembranipora Jacroi.i'ii ( ':} BUSK, Description of new Polyzoa, Quarterly Journal of 



Microscopical Science, vol. 8. p. 282. 



1861. ilembranipora irregitlaris BVSK, Description of new Polyzoa, Quarterly Journal of 



Microscopical Science, vol. 9 (n. s. vol. 1), p. 77, pi. 33, fig. 3 (not d'Orbigny). 



Description. The zoarium incrusts pebbles, shells, foraminifera, and other 

 bryozoa. The zooecia are elongated, distinct, oral, or elliptical with frequently a 

 very small gymnocyst; the mural rim is very prominent, curved, thin at the top, 

 enlarged at the base, finely granular. The opesium is elliptical, entire. The ovicell 

 is globular, prominent, deeply excavated, and separated from the mural rim. The 

 avicularium is interzooecial, as large as a zooecium; the mural rim is thick; the 

 pivot is median and solid. 



Measurements. Opesia 



0=0.32-0.36 mm. . \Lz=0.50 mm. 

 /ooecia , 



1o= 0.20-0.22 mm. lfe=0.32-0.40 mm. 



Variations. Examples of total regeneration are numerous and manifest them- 

 selves by their double mural rims. Figure 13 contains even a case of triple regen- 

 eration. The ancestrula is rather small and of normal form. Closed zooecia per- 

 forated by a small, round, medium pore, are located close to the ancestrula (fig. 15). 



The micrometric dimensions are identical with those of Membranipora crassi- 

 marginata relying upon the figure given by Waters. The only difference from 

 the recent species that we can cite is that in the latter the pivot of the avicularium is 

 placed irregularly. On such a trifling difference we can not distinguish another 

 species. 



Grammetia crassimarginata exists to-day in the waters off the Madeira Islands. 

 Its existence in the recent and ancient Gulf of Mexico is therefore very probable. 



Occurrence. Middle Jacksonian (Castle Hayne limestone) : Wilmington. 

 Xorth Carolina (very rare). 



