126 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 148 



Page 

 Figs. 12-14. Cheilocephalus, sp. undet 104 



12, Cranidium, X4. 13, 14, Pygidia, X4 (coll. cnr/4) ; U.S.N.M. 144711. 



Figs. 15-23. Aphclaspis zvashburnensis Rasetti, n. sp 85 



15-17, Dolsal, lateral, and frontal views of cranidium, x2 (coll. cnqV 



20) ; U.S.N.M. 144655, holotype. 18, Cranidium, xl.5. 19, Free cheek, 



X4. 20, Pygidium, x2 (coll. cnq720) ; U.S.N.M. 144656, paratypes. 



21, 22, Partly exfoliated cranidium, X3. 23, Pygidium, x3 (coll. ens/ 



15) ; U.S.N.M. 144657, paratypes. 



Plate 18 



Figs. 1-9. Aphelaspis quadrata Resser 78 



1-3, Small cranidium, X4. 4, Exfoliated free cheek, X2. 5, Free cheek, 

 X2. 6, 7, Exfoliated pygidia, X3. 8, Pygidium, x4 (coll. cns/16) ; 

 U.S.N.M. 144637, plesiotypes. 9, Pygidium, x4 (coll. U.S.N.M. 120; 

 U.S.N.M. 144638, plesiotype. 



Figs. 10-20. Aphclaspis walcotti Resser 76 



10, Cranidium, X3. 11, Free cheek and partly exfoliated cranidium, x4. 

 12, Exfoliated pygidium, x2. 16, Cranidium, x4 (coll. cnq/16) ; U.S.- 

 N.M. 144632, plesiotypes. 13-15, Lateral, frontal, and dorsal views of 

 cranidium, X2. 20, Pygidium, x3 (coll. cnq/20) ; U.S.N.M. 144633, 

 plesiotypes. 17, Free cheek, x3. 18, Pygidium, X4. 19, Free cheek, 

 X2 (coll. cnr/15) ; U.S.N.M. 144634, plesiotypes. 



Figs. 21-29. Aphelaspis punctata Rasetti, n. sp 92 



21, 22, 24, Frontal, dorsal, and lateral views of cranidium, X4 (coll. 

 cnw/14) ; U.S.N.M. 144673, holotype. 23, Cranidium, x4 (coll. cnw/ 

 14) ; U.S.N.M. 144674, paratype. 25, 29, Free cheeks, X4. 26, cranid- 

 ium, X3. 27, Cranidium, x4. 28, Pygidium, x5 (coll. cnw/20) ; U.S.- 

 N.M. 144675, paratypes. 



Plate 19 



Figs. 1-7. Aphelaspis tumifrons Resser 91 



1, 2, Dorsal and frontal views of cranidium, x4. 3, 4, Lateral and dorsal 

 views of cranidium, x4. 5, Free cheek, X4. 6, 7, Pygidia, x4 (coll. 

 cnt/4) ; U.S.N.M. 144672, plesiotypes. 



Figs. 8-17. Aphelaspis inermis Rasetti, n. sp 90 



8, 9, Frontal and dorsal views of cranidium, x4 (coll. cns/2) ; U.S.N.M. 

 144669, holotype. 10-12, Dorsal, lateral, and frontal views of cranidium, 

 X4. 13, Frontal view of large, partly exfoliated cranidium, X2. 14, 

 Dorsal view of the same specimen, X3. 15, Free cheek, X3 (coll. ens/ 

 2) ; U.S.N.M. 144670, paratypes. 16, Pygidium, X4. 17, Cranidium, 

 X2 (coll. cns/4) ; U.S.N.M. 144671, paratypes. 



Figs. 18-25. Aphelaspis minor Rasetti, n. sp 89 



18-20, Dorsal, frontal, and lateral views of cranidium, x4 (coll. cnq/ 

 17) ; U.S.N.M. 144665, holotype. 21, Cranidium, X4. 22, 23, Frontal 

 and dorsal views of cranidium, X4. 24, Pygidium, x4 (coll. cnq/14) ; 

 U.S.N.M. 144667, paratypes. 25, Free cheek, x4 (coll. cnq/15) ; U.S.- 

 N.M. 144668, paratype. 



Plate 20 



Figs. 1-18. Aphelaspis tarda Rasetti, n. sp 79 



5, Several cranidia, the one at left preserving one free cheek being the 

 holotype, X3. 6, Cranidium, X5; U.S.N.M. 144639, holotype. 1, Num- 



