470 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 53 



PACE 



nundina, see Syntrophia. 



nyssa, see Micromitra (Iphidclla). 



Obolacea, classification of 142 



defined 143 



Obolella, classification of 142, 145 



evolution of pi. 11 (pp. 140-141) 



shell structure of 149 



crassa, mentioned 79 



thin section of 165, pi. 12, fig. 10 



lindstromi, mentioned 264 



mobergi, mentioned 264, 290 



vermilionensis, mentioned 300 



sp. undt., stratigraphic position and association 186, 187 



Obolella (Glyptias), classification of 142, 145 



evolution of pi. 11 (pp. 140-141) 



Obolella (Glyptias) favosa, mentioned 290 



Obolellidje, classification of 142 



defined 145 



diagram showing line of descent 140 



distribution in Cambrian strata 140 



number of genera referred to the family 141 



Obolidse, classification of 142 



defined 143 



diagram showing line of descent 140 



distribution in Cambrian strata 140 



number of genera, species, etc., referred to the family with note on 

 distribution 141 



Obolinse, classification of 142 



defined 143 



Obolus, classification of 142, 144 



compared with Dcarbornia 79 



Elkania and Obolus (Fordiiiia') 65 



Neobolus 72i, 74. 76 



cruralium in 159 



evolution of pi. 11 (pp. 140-141) 



rnentioned 61, 64, 66, 79 



shell compared with that of Lingula 149 



trapezoidal area of 159 



Obolus apollinis, compared with Neobolus y^ 



microscopic shell structure of 152 



thin sections of 151, 165, pi. 12, figs. 11 and 12 



Oboltts discoideus, compared with Obolus zvortliciii 64 



stratigraphic position and association 193 



Obolus fcistmanteli, compared with Obolus membranaceous 61 



Obolus lamborni, compared with Obolus smitJii 63 



Obolus incconnelU, stratigraphic position and, association. ... 196, 197, 209, 210 



Obolus inccoiinelli prlias, stratigraphic position and association. . 176, 179, 180, 



i8r, 194 



