436 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 53 



Aero fret a — Continued. page 



rudis, new species 95» pl- 9, fig- 5 



compared with Acrotrcta dcfinila 96 



Acrotreta depressa 96 



sagittalis, compared with Acrotreta hcUaiula 94 



sagittalis taconica, mentioned 318 



stratigraphic position and association 213, 215 



ulrichi, new species 96, pl- 9> fig- 3 



compared with Acrotrcta curz'ata 96 



sp. undt., stratigraphic position and association 192, ig8 



Acrotretacea, classification of 142 



defined 146 



Acrotretidse, classification of 142 



defined '146 



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 



Acrotretinas, classification of 142 



defined 146 



acuminata, see Glossina, Lingula, Lingula (Glossina), and Lingulella 

 (Lingulepis) . 



acuminata seguens, see Lingulella {Lingulepis'). 



acutangula, see Anomalocaris and Lingulella. 



Adductor muscles, defined 154, i55 



adamsi, see Orthotheca. 



aquivalvis, see Orthis. 



Agassiz, Alexander, bibliographic reference 372 



on the habits of young Liinulus 241 



agues, see Olenopsis. 



Agnostus, intergenal spines in 237 



bidens, stratigraphic position and association 181 



graniilatus Barrande, intergenal spines of 237 



montis, stratigraphic position and association 211 



cf. montis, stratigraphic position and association 209 



pisiformis zone, mentioned 14 



rex, intergenal spines of 237 



sp. undt., stratigraphic position and association 176, 178, 179, 180, 



181, 192, 193, 194, 197, 199, 204, 205, 208, 210 



Agraulos, mentioned 318, 348 



stratigraphic position and association. .. .175, 177, 189, 194, 195, 210, 212, 



213, 214, 215 



Alabama, young cephalon of Pcedeuinias traiis'taus horn described. .. .308, 309 



Alberta, boundary of Cambrian land area in 169 



correlation of pre-Cambrian in with that of Montana 430-431 



future work in 2 



geologic and topographic map of Bow Valley pl. 47 



location of Cambrian sections measured i 



Lower Cambrian conglomerate found in 423-424 



