NO. 7 PTYCHOPARIID TRILOBITES — RASETTI 33 



1951. Middle Cambrian stratigraphy and faunas of the Canadian Rocky 

 Mountains. Smithsonian Misc. Coll., vol. 116, No. 5, pp. 1-277. 

 Resser, C. E. 



1935- Nomenclature of some Cambrian trilobites. Smithsonian Misc. Coll., 



vol. 93, No. 5, pp. 1-46. 

 1936. Second contribution to nomenclature of Cambrian trilobites. Smith- 

 sonian Misc. Coll., vol. 95, No. 4, pp. 1-29. 

 1937a. Third contribution to nomenclature of Cambrian trilobites. Smith- 

 sonian Misc. Coll., vol. 95, No. 22, pp. 1-29. 

 1937b. Elkanah Billings' Lower Cambrian trilobites and associated species. 



Journ. Paleont., vol. 11, pp. 43-54. 

 1938. Cambrian system (restricted) of the southern Appalachians. Geol. 

 Soc. Amer. Spec. Pap. 15, pp. 1-130. 



EXPLANATION OF PLATES 



Plate i 



Cranidia of nine genera of Lower Cambrian ptychopariid trilobites 



Page 



Fig. I. Antagymis gigas Rasetti 10 



Fig. 2. Eoptychoparia normalis Rasetti I4 



Fig. 3. Onchocephalus siilcatus Rasetti I7 



Fig. 4. Luxella lux (Walcott) 21 



Fig. 5. Ausihnnllia virgmica Resser 23 



Fig. 6. Perioimna walcotti Resser 24 



Fig. 7. Bicella bicensis ( Resser) 26 



Fig. 8, 9. PeriommcUa yorkensis Resser (dorsal and lateral views) 29 



Fig. ID. Rimoiiskia typica Resser 3^ 



Plate 2 



Figs. 1-8. Antagmus gigas Rasetti, new species 10 



1-3, Dorsal, lateral, and frontal views of exfoliated cranidium, X i-5 

 (boulder G-15) ; U.S.N.M. No. 123855, paratype. 4, Incomplete, 

 exfoliated cranidium, X i-S (boulder G-15) ; U.S.N.M. No. 123855, 

 paratype. 5, Exfoliated cranidium, X i-5 (boulder B-5) ; U.S.N.M. 

 No. 123854, paratype. 6, 7, Frontal and dorsal views of small crani- 

 dium, X 4 (boulder B-s) ; U.S.N.M. No. 123853, holotype. 8, Portion 

 of same cranidium, X 7, showing surface ornamentation. 



Figs. 9, 10. Crassifimbra, species undetermined No. 2 20 



Lateral and dorsal views of cranidium, X4 (boulder B-i) ; U.S.N.M. 

 No. 123875. 



Figs. 11-16. Antagmus elongatus Rasetti, new species li 



11-13, Dorsal, frontal, and lateral views of cranidium, X4 (boulder 

 M-io) ; U.S.N.M. No. 123856, holotype. 14, Small cranidium, X 6 

 (boulder G-41) ; U.S.N.M. No. 123857, paratype. 15, Cranidium, 

 X 6 (boulder G-17) ; U.S.N.M. No. 123857, paratype. 16, Free cheek, 

 X4 (boulder G-41) ; U.S.N.M. No. 123857, paratype. 



