EXPLANATION OF PLATES 

 Plate 1 



Page 



Figs. 1-4. Coosella andreas (Walcott) 48 



1, Cranidium, x4. 2-4, Dorsal, lateral, and posterior views of pygidium, 

 X4 (coll. cnc/2) ; U.S.N.M. 144572, plesiotypes. 



Figs. 5-7. Coosella resseri Rasetti, new name 48 



5-7, Lateral, posterior, and dorsal views of pygidium lacking test, x2 

 (coll. cnd/1) ; U.S.N.M. 144573, plesiotype. 



Figs. 8, 9. Kormagnostus simplex Resser 38 



8, Cephalon, xS. 9, Pygidium, x5 (coll. cnc/S) ; U.S.N.M. 144546, 

 plesiotypes. 



Figs. 10-12. Ithycephalus typicalis Resser 106 



10-12, Dorsal, lateral, and anterior views of cranidium, x5 (coll. 

 cnd/1) ; U.S.N.M. 144714, plesiotype. 



Figs. 13-21. Modocia bidentata Rasetti, n. sp 108 



14-16, Dorsal, lateral, and posterior views of pygidium, x2 (coll. 

 cnd/1) ; U.S.N.M. 144717, holotype. 13, Cranidium, xl.5. 17, Pygid- 

 ium, x2. 18, Cranidium, x2. 19-21, Dorsal, frontal, and lateral views 

 of cranidium, x2 (coll. cnd/1) ; U.S.N.M. 144718, paratypes. All 

 specimens lacking test. 



Figs. 22-26. Modocia dubia (Resser) 107 



22, 23, Dorsal and lateral views of cranidium, x2. 24, Free cheek, x2. 

 26, Pygidium, x2 (coll. cnc/5) ; U.S.N.M. 144715, plesiotypes. 25, 

 Exfoliated cranidium, x2 (coll. cnd/1) ; U.S.N.M. 144716, plesiotype. 



Figs. 27-30. Modocia? agatho (Walcott) 110 



27, 28, Lateral and dorsal views of cranidium, x4 (coll. cnc/5) ; U.S.- 

 N.M. 144724, plesiotype. 29, Pygidium, x3 (coll. cnc/2) ; U.S.N.M. 



144725, plesiotype. 30, Cranidium, x4 (coll. cnc/4) ; U.S.N.M. 



144726, plesiotype. 



Plate 2 

 Figs. 1-9. Modocia crassimarginata Rasetti, n. sp 109 



1-3, Dorsal, lateral, and frontal views of cranidium, x2 (coll. cnc/2) ; 

 U.S.N.M. 144719, holotype. 4, 5, Exfoliated cranidia, x2 (coll. 

 cnc/1) ; U.S.N.M. 144721, paratypes. 6, 7, Dorsal and posterior views 

 of pygidium, x2 (coll. cnc/3) ; U.S.N.M. 144722, paratype. 9, Ex- 

 foliated pygidium, x2 (coll. cnd/1) ; U.S.N.M. 144723, paratype. 

 8, Partly exfoliated cranidium, x2 (coll. cnd/1) ; U.S.N.M. 144723, 

 paratype. 

 Figs. lChl8. Bonnet errina appalachia (Walcott) 102 



10, Large cranidium, xl-5 (coll. cnc/6) ; U.S.N.M. 144703, plesio- 

 type. 11, 12, Dorsal and lateral views of cranidium with strong relief, 

 X2 (coll. cnc/5) ; U.S.N.M. 144704, plesiotype. 13, Free cheek, x2 

 (coll. cnc/5) ; U.S.N.M. 144704, plesiotype. 14, 15, Dorsal and lateral 

 views of pygidium, x4 (coll. cnc/1) ; U.S.N.M. 144705, plesiotype. 

 16, 17, Lateral and dorsal views of cranidium with weak relief and 

 shallow occipital furrow, x2 (coll. cnd/1) ; U.S.N.M. 144706, plesio- 



118 



