32 PROCEEDINGS OF THE NATIOISTAL MUSEUM vol.72 



The mural rims are generally separated. They are thick, but when 

 they are covered over by the ectocyst they appear thin. The inter- 

 zooecial avicularium is large. 



Affinities. — This species must not be confused with Membranipora 

 plana Hincks, 1880, of which we have discovered beautiful specimens 

 at Oran and in which the micrometric measurements are much larger ; 

 nor with Callopora parvirostris Canu and Bassler, 1923, of the Amer- 

 ican Miocene, in which the avicularium is very small. Waters illus- 

 trated the mandible in 1885 and the operculum in 1898. We add 

 the ancestrula. Our specimens encrust corals, shells, and Cellepores. 

 Biology. — Our specimens were living and in reproduction January 

 30, 1885. This is a species of waters of little depth from 10 to 89 

 meters, but because of its great vitality it is probable that it can 

 adapt itself to less favorable bathymetric conditions. 



Occurrence. — Albatross Station D. 2365, east of Yucatan; 22° 18' 

 GO'' N.; 87° 04' 00" W.; 24 fms.; white rock coral. 

 Albatross Station D. 2405, Gulf of Mexico; 28° 45' 

 00" N.; 85° 02' 00" W.; 30 fms.; gray sand, broken 

 coral. 

 Albatross Station D. 2639, Straits of Florida; 25° 04' 

 50" N.; 80'° 15' 10" W.; 56 fms.; coral sand. 

 Geologic distribution. — Eocene (Priabonian) of the Vicentin (Waters) ; 

 Oligocene of Anguilla (Canu and Bassler) ; Jacksonian of Mississippi 

 (Canu and Bassler); Helvetian of Tourraine (Canu); Pliocene of 

 Italy (Waters). 



CALLOPORA CURVIROSTRIS Hincks, 1861 



Plate 3, Figures 9, 10; Plate 32, Figure 8 



1903. Membranipora guernei Jullien, Bryozoaires provenant des campagnes 

 de I' Hirondelle (1886-1888). Resultats des Campagnes scientijaques 

 du Prince de Monaco, fasc. 23, p. 40, pi. 5, fig. 3. 



1918. Membranipora curvirostris Waters, Bryozoa of the Cape Verde Islands. 

 Journal Linnean Society, Zoology, vol. 34, p. 9. (Bibliography.) 



1923. Callopora guernei Canxt and Bassler, North American Later Tertiary 

 and Quaternary Bryozoa. Bull. 125, U. S. National Museum, p. 42, 

 pi. 45, figs. 3, 4. 



, r\ ' [Ao = 0.45mm. 

 Measurements. — Opesiau „ __ _ .„ 



^ Uo = 0.35-0.40 mm. 



fL2 = 0.50-0.55 mm. 



Zooeciau ^ ._ _ . _ 



U2 = 0.40-0.45 mm. 



Variations. — Our specimens encrust shells and large dead colonies 



of Stylopoma spongites. Above each avicularium there is frequently 



a curious uncovered space very irregular in form. It is difficult to 



explain the formation and the origin of these spaces. Waters, 1918, 



thought that they must be considered as aborted zooecia. In their 



more perfect form they appear to us to be the unoccupied portion of 



