458 BULLETIN 100, UNITED STATES NATIONAL MUSEUM 



Family ONCHOPORIDAE Busk, 1884 



The zoarium is free, continuous ramified, flexible. The zooecia 

 are slightly calcified; they are decorated exteriorly by apertural 

 septulae and frontal septulae, grouped or not in special areas. The 



Fig. 189a. — Genus Sclerodomus Levinsen, 1909 



A-G. Sclerodomus denticulatus Busk, 1884. A. Zoarium, natural size. B. 

 Part of a zoarium. The peristome is funnel-shaped, immersed, not projecting, 

 provided with avicularia; no peristomial pore. (After Busk, 1884.) C. A 

 sagittal section through some ovicellarian zooecia. The avicularium is seen on 

 the internal surface of the peristome and the plate originating from the distal 

 wall; X23. D. A sagittal section, X40. The distal wall is provided with an 

 expansion ending in a thickened, crenulated margin, which partly separates the 

 ovicell from the zooecium. The operculum is membraneous and feebly chitinized. 

 E. Longitudinal section showing the ovicell above the oral aperture, X'25. 

 (After Waters, 1889.) F. An ovicell ami ils surroundings, seen from the frontal 

 surface, X 40. (C-E after Levinsen, 1909.) G. Mandibles of the avicularium, 

 X85. (After Waters, 1904.) 



ovicell is hyperstoinial, generally closed by the operculum. The 

 ascopore, generally present, is crescentic. 



The genera of this family, in which the larva is unknown, are 

 based on zoarial differences. The secondary characters added to 

 differentiate 4hem will probably be insufficient when the number of 

 known species is greater. 



