456 BULLETIN 100, UNITED STATES NATIONAL MUSEUM 



Genus SCLERODOMUS Levinsen, 1909 



The peristome is funnel shaped, immersed, not projecting, provided 

 with avicularia; no peristomial pore; in the ovicelled zooecia the 

 distal wall is provided with an expansion ending in a thickened 

 crenulated margin, which partly separates the ovicell from the 

 zooecium. Operculum chitinized. 



Genotype. — Scle/odomus (Bifaxaria) denticulatus Busk, 1884. 



Fig. 188. — Genus Hvxleya Dyster, 1858 

 Huxleya fragilis Dyster, 1858. (After Busk, 1852.) 



Genus SYSTENOPORA Waters, 1904 



The aperture is suborbicular, transverse, without operculum. 

 The peristomice is auricular; it is a longitudinal slit placed between 

 two lateral lamellae, one concave and the other convex with a proxi- 

 mal avicularium. There is an avicularium in the peristomie and also 

 small zooecial avicularia; 20 tentacles. The colonies are free and 

 radicellate. 



Genotype. — Systenopora contractu Waters, 1904. Recent (Northern 

 Hemisphere). 



