KORTH AMERICAN EAULV TERTIARY BRYOZOA. 779 



1000. Idmnnca atlantica NEVIANI, Monographia del genere Idmonea Bryozoa C'iclostomata. 

 pt. 1, pp. 0, 46 (synonomy) ; 1901, pt. 2, cap. 2, p. 74. 



1903. Iilni'iiK-n ntlaiiticn .In.i.iFN and CAIAET. Resultats des Canipagnes seientifiques du 



Prince du Monaco, Fascicule 23, p. 113. 



1904. Iiliniini'ii uttaiiUca WATERS, Bryozoa from Franz-Josef Land. pt. 2. Journal Liunean 



Society, Zoology, vol. 29, pp. 166, pi. 21, figs. 2, 3 (the ovicell here figured is un- 

 usually short). 



1904. Idmonca atlantica WATERS, Bryozoa Resultats voyage Kclijica, Zoologica, p. 90, 

 pi. 9, fig. 5. 



1906. Idmoncii atlantica NORDGAARD. Bryozoa from the 2d Fram Expedition, 1898-1902. 



Report Second Norwegian Arctic Expedition 1S9S-1902, No. 8, p. 38. 



1907. Idmonca atlantica CALVET, Note par les expeditions du Travailleur et Talisman, 



vol. 8, p. 469. 



1909. Idmonva atlantica NORMAN. The Polyzoa of Madeira and neighboring Islands, Jour- 

 nal Linnean Society. Zoology, vol. 30, p. 278, pi. 33, figs. 1. 2. 

 1912. Idmonea atlantica THORNELV, Marine Polyzoa of the Indian Ocean, Transactions 



Liuneau Society, Zoology, ser. 2, vol. 15, p. 156. 

 1912. Tubulipora atlantica OSBURN, The Bryozoa of the Woods Hole Region, Bulletin of 



the Bureau of Fisheries, vol. 30, 1910, p. 217, p. 19, figs. 9, 9<z. 

 18S6. TubuUpora atlantica. forma erecta SMITT, Kritisk forteckning ofver Skandinaivens 



Hafsbryozoer, Ofversigt af. Kongl. Vetenskaps-Akademiens Fordhandlingar, vol. 23, 



pp. 399, 434, pi. 3, figs. 6-7. pi. 4, figs. 3-13 (ovicell figured). 

 1S49. Idmonca radians VAN BENEDEN, Recherches sur les Bryozoaires de la mer du nord 



(suite) et projet d'une classification des Bryozoaires, Bulletin ]' Academic Royale 



de Belgique, vol. 16. p. 646. pi. 1, figs. 4-6. 

 1916. Tubulipora atlantica HARMER, The Polyzoa of the Siboga expedition, vol. 1, p. 124, 



pi. 10, figs. 4-5. 



Description. The zoarium is free, linear, bifurcated, with subcircular trans- 

 verse section. The fascicles are salient, quite removed from the median crest, 

 arranged alternately on each side of it, much protruding beyond the zoarial mar- 

 gins; they are formed of three to five zooecia the first of which is the longer and 

 hides the others more or less. The basal lamella is somewhat striated longitudi- 

 nally by the tubes, striated transversally by quite separated convex wrinkles; it is 

 round or flat and more or less bordered laterally. The ovicell is much elon- 

 gated, convex, scarcely lobed, placed on the median crest among five or six fasci- 

 cles. 



Distance between the fascicles 0.48 (0.40-0.60 mm.). 



Width of the fascicles 0.14 mm. 



Width of the zoarium 0.60 (without the fascicles). 



Variations. The dorsal is round at the base of the branches (fig. 9) and flat 

 on the younger branches (figs. 7, 8) ; the two forms are often visible on the same 

 branch (fig. 4). The fascicles are quite fragile and break easily (fig. 6) ; but the 

 fossils thus altered are exceedingly difficult of determination and are almost iden- 

 tical with the linear branches of Idmonea petri D'Archiac, 1847. 



In a single instance only have we observed a very short radicell (fig. 10). 



The tangential (fig. 12) and longitudinal sections (figs. 11) offer no special 

 features ; but the transverse section has a very special form, for it is almost circular 

 or semicircular according to the form of the dorsal. 



Measurements. 



