202 BULLETIN 125, UNITED STATES NATIONAL MUSEUM. 



Affinities. — This species differs from Mesenteripora meandrina Robertson, 1910, 

 in the ovicell not placed near the zoarial margin, and in its tubes grouped in fascicles. 



In spite of exterior appearances the tubes are not arranged as in Reticulipora, 

 the axis of the apertura being placed in the longitudinal axis of the zooecia. 



Occurrence. — Pleistocene: Santa Barbara (conunon), and Santa Monica 

 (Rustic Canyon), California (rare). 



Cotypes. —Cat. Nos. 6S747, 68748, U.S.N.M. 



Genus DIAPEROECIA Canu, 1918. 



(For description, see Bvilletin 106, U. S. National Miiseum, p. 740.) 



DIAPEROECIA FLABELLATA, new species. 



Plate 43, figs. 18, 19. 



Description. — The zoarium is free, bilamellar and formed oi jlabelTate fronds, 

 and irregularly twisted. The tubes are little visible, widened at their extremity; 

 the peristome is thin, salient, elliptical, horizontal. The ovicell is convex, smooth, 

 traversed by 6-10 tubes; the oeciostome is crescentric and joined to an ordinary 

 peristome. 



Measurements. — 



Diameter of the peristome 0. 15 mm. 



Distance between the peristomes 0. 42-0. 50 mm. 



Separation of the peristomes _ , 0. 50-0. 55 mm. 



Occurrence. — Pleistocene: Santa Monica (Tremochal Canyon) (rare), and 

 Dead Mans Island, off San Pedro, California (very rare). 

 Holotype.~Cat. No. 68749, U.S.N.M. 



DIAPEROECIA MILNEANA D'Orbigny, 1839. 



Plate 6, figs. 20, 21. 



1839. Idmonea milneana D'Orbigny, Vcj'age dans L'Am^rique M^ridionale, vol. 5, pt. 4, p. 20, 

 pi. 9, figa. 17-21. 



1919. Idinonea milneana Canu and Bassler, Geology and Paleontology of the West Indies, Bryozoa, 



Publications of the Carnegie Institution of Washington, No. 291, p. 99, pi. 6, figs. 20, 21. 



1920. Idmonea milneana Canu and Bassler, North American Early Tertiary Bryozoa, Bulletin 



106, U. S. National Museum, p. 773, pi. 136, figs. 1-12. 



This recent species has been identified in a nimiber of Tertiary formations 

 of Europe and in the Jacksonian and Vicksburgian of North America. So far 

 the only discovery of it m the post-Oligocene strata of North America is in the 

 Lower Miocene of Santo Domingo, where the smgle specimen here illustrated has 

 been found. 



The discovery of nimierous ovicelled specimens of this species in dredgings 

 from the Gulf of Mexico cause us to refer it generically as above. 



Occurrence. — Lower Miocene (Bowden horizon) : Cercado de Mao, Santo Do- 

 mingo (rare). 



Plesiotype.—C&t. No. 68750, U.S.NTM. 



