EXPLANATION OF THE PLATES. 83 
Fig. 10.—a, 6.’ PLECTRODUS PUSTILIFERUS, Agassiz, sp. 
Sclerodus, Sil. Syst., pl. iv., figs. 27-32, 60-62. Plectrodus, Sil., 4th ed., 
pl. xxxv., figs. 9-12. 
a. Natural size; 6. enlarged. From the figures in Sil. Syst., pl. iv., figs. 28, 31. 
Upper Ludlow, Bone-bed, Ludford, near Ludlow. 
LupLow.—Sil., 4th ed., p. 536. 
Fic. 11.—a, J, e. THEGLODUS PARVIDENS, Agassiz. 
Sil. Syst., pl. iv., figs. 34-36. Sil., 4th ed., pl. xxxv., fig. 18. 
a, b, ec. Natural size and enlarged, granulesof the skin or shragreen of Onchus ? 
From the figures in Sil. Syst., pl. iv., figs. 34-36. ‘‘They occur by 
myriads.” Sil., 4th ed., p. 241. Upper Ludlow, Bone-bed, Ludford, 
near Ludlow. 
Luptow.—Sil., 4th ed., p. 536. 
