NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
89 
i 
CONOPEUM LACROIXII Busk, 1852. 
Plate 13, fig. 9. 
1826. Flustra lacroixii Audouin, Explication sommaire des planches de Polypes de l’Egypte 
et de la Syrie, in Savigny’s Description de l’Egypte. Histoire Naturelle, pi. 10, 
flg. 9. 
1852. Membranipora lacroixii Bxjsk, Catalogue Marine Polyzoa, pt. 1. Cheilostomata, p. 
60, pi. 49 and pi. 104, flg. 1. 
1880. Membranipora lacroixii Hincks, British Marine Polyzoa, p. 129, pi. 17, figs. 5~8. 
1900. Membranipora lacroixii Robertson, Papers from the Harriman Alaska Expedition, 
6, The Bryozoa, Proceedings, Washington Academy Science, vol. 2. p. 323. 
1907. Membranipora lacroixii Canu, Bryozoaires des terrains tertiaires des environs de 
Paris, Annales Paleontologie, vol. 1, p. 8. 
1908. Membranipora lacroixii Robertson, The Inerusting Cheilostomatous Bryozoa of the 
West Coast of North America, University of California Publications, vol. 4, p. 261, 
pi. 14, fig. 5. 
1908. Membranipora lacroixii Canu, Iconographie des Bryozoaires fossiles de l’Argentine, 
Anales del Museo Nacional de Buenos Aires, vol. 17, p. 251, pi. 1, figs. 8, 9. 
1912. Membranipora lacroixii Osburn, The Bryozoa of the Woods Hole Region, Bulletin 
Bureau Fisheries, vol. 30 (1910), p. 227, pi. 22, fig. 28. 
1913. Membranipora lacroixii Canu, Ifltude comparee des Bryozoaires Helvetiens de l’Egypte 
avec les Bryozoaires vivants de la Mediterranee et de la Mer Rouge, Memoires 
Institut Egyptien, vol. 6, p. 195, pi. 1, figs. 5, 6. 
Not Biflustra lacroixii Smitt, Floridan Bryozoa, pt. 2, Kongl. Svenska Vetenskaps-Akade- 
miens Handlingar, vol. 11, 1873, p. 18, pi. 4. figs. 85-88. 
The collections of American Tertiary bryozoa have yielded a number of ex- 
amples of this interesting species which is widespread in both the recent and 
ancient seas. 
Measurements. — Opesia 
|Ae>= 0.32-0.36 mm. 
I lo= 0.12-0.22 mm. 
Aooocia 
17.2=0.24 mm. 
It is not certain that the species described by Busk is that of Audouin. The 
synonymy of M embranipora reticulum given by Pergens in 1887 is absolutely fan- 
tastical. To avoid confusion, Canu in 1907 restricted the synonomy to the species 
described by Busk, including the living form and the few fossil specimens figured. 
This restriction is still insufficient, as we believe that it is necessary to classify as 
C onopeum lacroixii only those specimens having interopesial cavities with distinct 
walls and in which the average zooecial length does not exceed 0.40 mm. 
Variations and affinities. — This species presents two quite distinct aspects. 
First, the zooecia have their mural rims separated by a deep furrow, and the 
interopesial cavities are constant and provided with their own individual walls (see 
figure by Miss Bobertson). Second, the zooecia have their mural rims adjacent to 
each other and their interopesial cavities are present or absent (as figured by 
Osburn). 
In the living specimens these two variations occur on the same zoarium, but the 
first appears less frequently. Different species may take the second aspect when 
there are no interopesial cavities. This results in unusual difficulties in the deter- 
mination of the fossils and requires the greatest care for accurate identification. In 
