^^OETH AMERICAN LATER TEBTIAEY AND QUATERNARY BRYOZOA. 199 



IDMONEA PLANULA, new species. 



Plate 26, figs. 13-15. 

 Description.— The zoarium is free, wide, with semielliptical section; the dorsal 

 is flat and striated transversally. The fascicles are salient, opposite, quite close 

 but diverging from the median crest. The tubes are visible, separated by a little 

 salient thread, and number tliree or four to a fascicle; the peristomes are thm 

 and rectangular. 



Measurements.— Width of fascicles 0.20 mm. 



Distance between the fascicles 0.40-0.60 mm. 



Diameter (on the zoarium) of the first tube - 0.24 mm. 



Number of the tubes - - - 3-4. 



Width of the zoarium 1.20 mm. 



Affinities.— This species has the general aspect of Idmonea petri D'Archiac, 

 1846. It differs from it in a greater distance between the fascicles (more then 

 0.40 mm.) and in the larger zoarial dimensions. 



Occurrence.— Miocene (Choctawhatchee marl): Jacksons Bluff, Ocklocknee 

 River, 25 miles southwest of Tallahassee, Florida (very rare). 

 Holotype.— Cut. No. 68741, U.S.N.M. 



IDMONEA CALIFORNICA D'Orblgny. 1852. 



Plate 43, figs. 1-9. 

 1852. Idmonea califomica D'Orbigny, Paleontologie francaise, Terrains cr^tac^s, vol. 5, Bryozo- 



aires, p. 732. . . n i-t • 



1855. Idrmnea caUfomka Conrad, Xotes on Miocene and Post-PLocene deposits of California, 



Proceedings Academy Natural Sciences Philadelphia, vol. 7, p. 441. 

 1862 Idmonea califomica Gabb and Horn, Monograph Polyzoa, Secondary and Tertiary formations 



North America, Journal Academy Natural Sciences Philadelphia, ser. 2, vol. 5, p. 168, 



pi. 21, fig. 56. t -K- v A • 



1910 Idmonea califomica Robektson, Cyclostomatous Bryozoa of the west coast of I\orth America, 

 University of California Publications, Zoology, vol. 6, p. 253, pi. 23, figs. 39-41 (bibli- 

 ography). 



Measurements.— Di?cmeter of the orifice 0.20 mm. 



Diameter of the peristome - 0.28 mm. 



Width of the fascicles - -- 0.28 mm. 



Distance between the fascicles 0.80 mm. 



Variations.— TKis giant species seems to be restricted to the American shores 



of the Pacific. ■ j- i 



The fascicles are almost opposite. On the median axis there is a longitudmai 

 row of isolated tubes, often closed by a calcareous diapliragm. 



In tangential section the walls are perforated, but the perforations are no 

 lar<^er than in other species of Idmonea with small dimensions. In longitudinal 

 section the zooecial walls appear very thick. In transverse section the tubes 

 are rectangular. The ovicell is large, convex, placed on the median crest and 

 finely porous. It surrounds the isolated zooecia of the median axis, which gives 

 it the aspect of Diaperoecia, but it does not surround the fascicles and its inter- 

 fascicular lobes are very short. t i j «• -• 



Occurrfnce.— Pleistocene: Santa Monica (rare). Dead Mans Island, oh ban 

 Pedro (very common), and Santa Barbara, California (very common). 



Plesiotypes. —C&t. Nos. 68742, 68743, U.S.N.M. 



