78 PROCEEDINGS OF THE ^-ATIONAL MUSEUM vol.72 



Occurrence. — Albatross Station D. 2167, off Habana, Cuba; 23° 



10' 40" N.; 82° 20' 30" W.; 201 fms.; coral. 

 Albatross Station D. 2334, north of Cuba; 23° 10' 



42" N.; 82° 18' 24" W.; 67 fms.; white coral. 

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



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

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



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



coral. 

 Florida, 41-97 meters (Smitt) ; Tortugas, 8-24 meters 



(Osburn) . 

 Plesiotypes. —Csit. Nos. 7608, 7609, U.S.N.M. 



Family PETRALIIDAE Levinsen, 1909 

 Genus PETRALIELLA Canu and Bassler, 1927 



PETRALIELLA BISINUATA Smitt, 1873 



Plate 16, Figures 1-5; Plate 33, Figure 4; text Figures 12a-h 



1873. Escharella bisinuata Smitt, Floridan Bryozoa. Kongl. Svenska Veten- 

 skaps-Akademiens Handlingar, vol. 11, p. 59, pi. 12, fig. 229. 



1909. Petralia bisinuata Levinsen, Studies on the Cheilostomatous Bryozoa, 

 pp. 350, 351. 



1914. Petralia bisinuata Osburn, Bryozoa of the Tortugas Islands. Publi- 

 cation Carnegie Institution, Washington, No. 182, p. 217. 



,, ^ A ^ /?ia = 0.24-0.25 mm. 



Measurements. — Apertures 



^ Ua = 0.26 mm. 



ry . fi2 = 0.90-1. 15 mm. 

 Zooeciau _ _-. _ __ 



Us = 0.50-0.55 mm. 



Variations. — Smitt spoke only of a single avicularium; there are 

 generally two on our specimens; rarely are they equal, one being 

 larger than the other; these are the zooecial avicularia. Rarely 

 there are two avicularia on the shield; then there are no longer any 

 large avicularia. This irregularity is disconcerting and does not 

 permit us to judge the function of these small organs. 



The cribriform area is a rather deep concavity surrounded by a 

 peristome, closed by the ectoyst, where there are no radicells and 

 placed below the aperture. It is frequently accompanied by one or 

 two smaller radicular pores. The frontal structure is that of a 

 tremocyst. 



This is a rare species of which we were able to prepare the com- 

 plete operculum. It is often detached from the compensatrix, but 

 frequently the chitinization stops at the axis of rotation. The oper- 

 cula of the ovicelled zooecia are a little larger. The chitinized band 

 which surrounds the operculum is generally narrow, but it can become 

 enlarged as in the genus Petralia. 



