SHIDELERITES [S. typus] Morris and Hill 1951,p.698 [Bairdiidae 
by Betty Kellett Nadeau in footnote at end of 
Morris and Hill's paper,p.699] Silurian, Indiana. 
SIGMOBOLBINA [Entomis oblonga kuckersiana Bonnema 1909, 
pe67,pl.5,f-6-8 (not fige9)] Henningsmoen 1953, 
p.e206-208 [Sigmoopsiidae-Sigmoopsiinae by Hennings- 
moen] Ordovician drift, Germany. 
SIGMOOPSIIDAE Henningsmoen 1953,p.201,266, a family of 
Beyrichiacea, with subfamilies Sigmoopsiinae and 
Glossopsiinae. 
SIGMOOPSIINAE Henningsmoen 1953,pe203,266, a subfamily of 
Sigmoopsiidae to include Sigmoopsis, Ogmoopsis, 
Sigmobolbina, Carinobolbina, Bolbina, ?Kiesowia, 
?Ctenobolbina, and ?2Winchellatia. 
SiGMOOPSIS [Ceratopsis platyceras Opik 1937,p.99,pl.2,f.6,7] 
Henningsmoen 1953,pe204,266 [ Sigmoopsidae-- 
Sigmoopsiinae by Henningsmoen]} Ordovician, Estonia. 
SIGYNUS [S. dictyotus] Kesling 1953c,pe4 [Aechminidae by 
Kesling] Devonian, Ontario. 
SILENITES {S. silenus] Coryell and Booth 1933,p.265 [Bair- 
diidae by C&B; Cytherellidae by Kellett 1935,p.150, 
but Bairdiidae by Kellett 1935,p.166 in note at 
end of paper] Pennsylvanian, Texas. [Silenites 
174 
