104 
The American Geologist, 
February, 1894 
joined by a simple or variously modified and complicated cal- 
careous loiip. 
I. Family ATRYPID/E, Dall 1887. 
Crura directly continuous with the primary lamelhe which 
diverge widely and have the spirals between them. Loop sim- 
ple, complete or incomplete; shell structure impunctate. 
A. Subfamily Zygospirin^, Waagen iss:;. 
Anazygida?, Davidson 1884. 
Loop a single connecting band either posteriorly or ante- 
riorly directed. Spirals usually introverted, with their apices 
toward the median dorsal region. 
Zygospira, Hall 1862. Catazyga, II. and C. 1893. 
Stenocisma, Hall 1874 (not Atrypime, II. and < !. 1893. 
Conrad 1839; Hall 18G7). Glassia, Davidson, 1882. 
Clintonella, II. and C. 1893. 
Anazyga, Davidson 1882. 
Orthonomaja, Hall 1858. 
Hallina, Winched and Schu- 
chert 1892. 
Protozyga, Hall and Clarke 
1893. 
B. Subfamily Dayix.e, Waagen 1883. 
Loop drawn out posteriorly into a simple short process. 
Spirals laterally directed. 
Dayia, Davidson 1882. 
A 1 . Subfamily Atryiux.e. Waagen 1883. 
Loop situated extremely posterior, complete in young- 
stages, but at maturity medially absorbed. Spirals dorso- 
medially directed. 
Atrypa, Dalman 1828. Grunewaldtia,Tschernyschew 
Cleiothyris, Phillips 1841 (not 1885. 
King 1830). v Karpinskya, Tsch. 1885. 
Spirigerina, d'Orbigny 1847. 
II. Family SPIRI FERID/C, King 1846 (emend Davidson). 
Martiaiiaaj and R3ticulariin;e, Waagen 1883; Spiriferinid;e, David- 
son 1884. 
Primary lamelhe directly continuous with the crura and 
situated between the laterally directed spirals, except in Cyclo- 
spira where they are somewhat introverted. Loop simple, 
complete or incomplete. 
