462 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 53 



PAGE 



Marcou, J., bibliographic references 375 



marion, see Billingsella. 



Marjum formation, correlated 171 



defined 10 



fossils from 33, 35, 39, 65, 77, 94, 95, 106, 109 



section of i79-i8i, pi. 15, figs, i and 2 



marjumensis, see Acrotreta. 



Marr, John E., bibliographic reference 375 



on the posterior segments of Mcsonacis vennontana and the telson 

 of Olenellus 313-314 



Matthew, G. R, bibliographic references 113, 218, 376 



on absence of Holmia kjerulii from New Brunswick collections. .. . 376 



matthczvi, see Acrothele. 



McConnell, R. G., bibliographic reference t 375 



mentioned i 



mcconnelli, see Oboliis. 



mcconnelli pelias, see Obolus. 



Median septum, defined i57 



Meek, F. B., bibliographic references 113, 162, 218 



membranaceous, see Obolus. 



Menocephalus, stratigraphic position and association 192, 210 



Mesonacidse Walcott 235 



abrupt appearance of 252 



alphabetic list of species assigned to 35I-37I 



anterior glabellar lobe in 242, 243 



cause of enlargement of third segment in 245 



cephalon, development of 236-244 



segmentation of 237-238 



delimitation of genera of 246 



development of 236-250 



from an Anellidian-like ancestor 249 



shown in diagram 249 



distinguished from the Paradoxinje 250 



eyes of 239 



facial sutures in 242 



fauna, name proposed 252 



first use of term and reasons for its use 2t,t, 



genal, intergenal, and antero-lateral spines in 237 



geographic distribution of 252-253 



hypostoma of 243-244 



maculae on hypostoma of 240-241 



possible occurrence in Siberia, Australia, Sardinia, Spain and 



France 253 



pygidium of 245-246 



stratigraphic position of the genera and species 250, 251 



thorax of discussed, defining various stages of development 244-245 



transition to Paradoxinse 253 



visual organs on hypostoma of 241-242 



