ZYGOBOLBA [Beyrichia decora Billings 1866,p.67 = Zyzobolba 
decora (Billings) Ulrich and Bassler 1923,p.537, 
pl.39,f0l15=22; plekO,fell-14; pl.64,f.21-25] 
Ulrich and Bassler 1923a,p.308 [Zygobolbidae-- 
Kloedeninae by U&B; Beyrichiidae-Zygobolbinae by 
Henningsmoen 1953,pe269] Silurian, Anticosti. 
ZYGOBOLBIDAE Ulrich and Bassler 1923a,p.30h, a family of 
Beyrichiacea, composed of the subfamilies: 
Zygobolbinae, Drepanellinae, and Kloedeninae. 
ZYGOBOLBINAE Ulrich and Bassler 1923a,p.e304, a subfamily of 
Zygobolbidae to include: Zygobolba, Zygobolbina, 
Zygosella, and Bonnemaia. 
ZYGOBOLBINAE of Henningsmoen 1953,p.238,269, a subfamily 
of Beyrichiidae to include: Zygobolba, Zygobolbina, 
Zygosella, Mastigobolbina, Plethobolbina, Bonnemaia, 
and ?Craspedobolbina. 
ZYGOBOLBINA [Z. conradi] Ulrich and Bassler 1923a,p.305 
[ Zygobolbidae-Zygobolbinae by U&B; Beyrichiidae-- 
Zygobolbinae by Henningsmoen 1953,p.269] Silurian 
of New York. 
ZYGOBOLBOIDES [Z. grafensis] Spivey 1939,p.169 [Zygobolbinae 
by Spivey; Zygobolbidae by Agnew 1942,p.761;3 
Drepanellidae-?Bolliinae by Henningsmoen 1953, 
pe268] Ordovician, Iowa. 
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