D.P. GORDON AND P.D. TAYLOR 
Figs 60-64 Onychocellid and aspidostomatid cheilostomes. 60-63, ?Onychocella sp., IGNS, BZ 210; 60, eroded colony showing disposition of 
autozooids, ovicellate zooids and vicarious avicularia, x 45; 61, vicarious avicularium and ovicellate zooid, x 95; 62, vicarious avicularium, autozooidal 
and ovicelled orifices, x 127; 63, ovicellate zooid (ovicell partly broken) and tip of avicularian rostrum proximally, x 116. 64, Aspidostoma litotes sp. 
nov., IGNS BZ 191, holotype, part of erect branch, x 53. 
Colony surface in the somewhat worn specimen rather featureless, 
with no trace of avicularia or other polymorphs. Peristomial and 
primary orifices more or less D-shaped or the proximal rim with a 
slight median convexity, 0.31—0.39 mm wide externally, 0.31—0.34 
mm wide internally at the level of the primary orifice, with an 
indication in some orifices that slight opesiular indentations at the 
proximal corners continue as grooves down the inside of the peristome 
on each side. No indication of ovicells. 
REMARKS. The generic affinities of this specimen are very ob- 
scure. The excessive thickness of the cryptocyst is reminiscent of 
Inversaria, but opesiae and orifices in Inversaria species are typi- 
cally subcircular and more centrally placed. More and 
better-preserved material is needed. 
