448 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 53 



PAGE 

 Deep Spring Valley, California, fossils in 81, 300, 323 



view of quartzite in pi. 18 



dcfinita, see Acrotreta. 

 degeeri, see Hyolithes. 

 Dclgadella, classification of 142, I44 



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



Delthyrium, defined 156 



Deltidium, defined 156 



Dental plates, defined 156 



Dental sockets, defined 156 



depressa, see Acrotreta. 



descendens, see Acrotreta ophirensis. 



desiderata, see Elkania and Lingnlella. 



Dicellocephalus, stratigraphic position and association 175, 191 



Dicellomns, classification of 142, 144 



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



mentioned 76 



parvus, new species 76, pi. 8, figs. 2 and 2a 



compared with Dicellomus poHtus 76 



politus, compared with Dicellomus parvus 76 



compared with Dicellomus proliUcus yy 



Obolns (Fordinia) gilberti 65 



proliiicus, new species 77, pi. 8, figs. 3 and 3a 



compared with Dicellomus politus yy 



stratigraphic position and association 179 



Dickhaut, Henry, acknowledgments 235 



Diductor muscles, defined 156 



Discina Miquel, in synonymy 83 



referred to Acrothele by Pompeckj yy 



Discinacea, classification of 142 



defined 146 



Discinella, mentioned 279 



Discinidse, classification of 142 



defined 146 



diagram showing line of descent 140 



distribution in Cambrian strata 140 



Discinolepis, classification of 142, 146 



evolution of pi. 11 (pp. 140-146 



Disciiiopsis, classification of 142, 146 



compared with Dearhornia 80 



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



discoideus, see Obolus. 



Dolicliometopus occidentalis = Bathyuriscus occidcntalis 41 



Dome Canyon, House Range, view of pi. 16 



Dome formation, correlated 171 



defined 11 



section of 182, pis. 16 and ly 



Dorsal valve, defined 156 



Dorypyge quadriceps, stratigraphic position and association 196 



