144 BULLETIN 100, UNITED STATES NATIONAL MUSEUM 



Variations. — Our specimens were numerous and living; the varia- 

 tions shown by them are important. The central zooecia are never 

 calcified on the small colonies but become calcified when the zoarium 

 increases in size. The zooecia are very irregular in dimensions and 

 form; some are very elongated and others are transverse. The 

 number of opesiules is from 8 to 9. The vestibular arch is very 

 constant. 



On the interior face the radial ribs are not always clearly visible. 

 At the center the tuberosities are hollow; they are solid at the middle 

 and very thin along the border. This arrangement is a little differ- 

 ent from that which is ordinarily observed on specimens from the 

 Atlantic. The interior face is formed of many irregularly super- 

 posed and juxtaposed disks. We have already published the same 

 observation for the fossil forms from the Antilles. 



When the frontal is broken the zooecial aspect is in effect that of 

 Cupulariahaidingeri Reuss, 1847, or of Cupularia denticulata Conrad, 

 1841; but the microscopic examination shows clearly that the visible 

 spicules are broken and not fringed and denticulated as in these 

 two species. 



Biology. — This species has been dredged in very great depths and 

 it is one of the rare species characteristic of the abyssmal ooze. On 

 account of its mobility it can live above the shifting sea floor. Its 

 bathymetric distribution arises only to 80 meters and it does not 

 appear to adapt itself easily to less depths of water (Calvet, 1907). 



Occurrence. — D. 2826. Pacific between California and the Hawaiian 

 Islands; 29° 50' 30" N.; 141° 40' E.; 2,723 fathoms; brown ooze. 



Geologic distribution . — Mediterranean : Oran (87 meters) . Atlantic : 

 Cape Verde Islands (1,900 meters) (Calvet), Canary Islands (80 

 meters) (Calvet), Florida (7-30 fathoms) (Smitt). Indian Ocean: 

 Mergui Archipelago (Hincks). 



Plesiotypes. —Cat. No. 7942, U.S.N.M. 



Family STEGANOPORELLIDAE Hincks, 1884 



See Canu and Bassler, 1920, for descriptions and illustrations of 

 the members of this family. 



Genus STEGANOPORELLA Smitt, 1873 



STEGANOPORELLA MAGNILABRIS Busk, 1854 



Plate 15, figs. 1, 2 



1923. Sleganoporella magnilabris Canu and Basslek, North American Later 

 Tertiary and Quaternary Bryozoa, Bull. 125, U. S. National Museum, 

 p. 63, pi. 14, figs. 12, 13 (Bibliography). 



1926. Sleganoporella magnilabris Harmer, Polyzoa "Siboga" Expedition, pt. 2, 

 p. 277, pi. 17, figs. 1-3, 7, 9, 12, text fig. 10. (Bibliography and ana- 

 tomical studies.) 



