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BULLETIN 100, UNITED STATES NATIONAL MUSEUM 



Genus RETIFLUSTRA Levinsen, 1909 



The distal wall, at any rate in the ovicelligerous zooecia, very 

 often also in the ordinary zooecia, meets with the basal wall in an 

 angularly bent or curved line. The free edge of the ovicells on the 

 frontal side of the colony lies much lower than the basal edge. The 

 avicularia have the same size as the zooecia. The zoarium much 

 branched dichotomously, with frequently the branches meeting and 

 thus forming an open network. Radical fibers occur in the angles of 

 the branches. (Levinsen). 



Genotype. — Retiflustra (Retepora) cornea Busk, 1852 (Carbasea 

 cribriformis Busk, 1852). 



Fig. 17. — Genus Flustra, subgenus Chartella 

 Gray, 1848 



A, B. Flustra (Chartella) papyracea Ellis and Solander, 1786. A. Zoarium, 

 natural size. B. Portion showing zooecia and ovicells. (After Hincks, 1890.) 



Genus SPIRALARIA Busk, 1861 



The lateral walls within the covering membrane generally with 

 numerous spinelike denticles. The margins of the zooecium have as 

 a rule more or fewer (occasionally numerous) spines. The avicularia 

 have generally a pointed mandible (Levinsen). 



Genotype . — Spiralaria jiorea Busk, 1861. 



Genus HETEROFLUSTRA Levinsen, 1909 



Artificial group for unplaced Flustridae. 



Family HINCKSINIDAE Canu and Bassler, 1927 



This family probably forms only a section of a more extended family 

 comprising the Flustridae and Farciminariidae, but as the larvae are 

 unknown we prefer not to make any more important changes in the 

 nomenclature. Hincksina Norman, 1903, Vibracellina, Ogivalina and 

 Membrendoecium Canu and Bassler, 1917, Antropora Norman, 1905, 

 and SetoseUina Calvet, 1907, of this family are described and illus- 

 trated in our work of 1920. 



