PLATE V. 



Fig. 



1 . Scales of Pteraspls sp., Perthshire. Mr. Powrie. 



2. Pleraspis Miic/ielii. View of the concave surface ; on the right hand is seen the 



internal aperture of the cornual perforation. Perthshire. Dundee Museum. 



3. Scales of Pteraspis sp., attached to a portion of the striated head-shield (see figs. 



7 and 8). Cradley, Herefordshire. Author's cabinet. 



4. Pt. rostratus. Cast of disc and rostrum, with cornua attached ; on the right-hand 



side the matrix is seen filling the hollow passage of the cornu, and surrounded 

 by bony matter. Cradley. Author's cabinet. 



5. Enlarged view of some of the scales of fig. 3, showing surface markings. 



6. Pt. Mitchelli, a specimen without the cornua and spine. Perthshire. Mr. 



Powrie. 



7. Magnified view of the striations of the part of the head-shield preserved in the 



specimen drawn in figs. 3 and 8. 



8. Side view of the specimen drawn in fig. 3. 



9. A huge Heterostracous head-plate, perhaps Scaphaspis Lloydii. Near Ludlow. 



Mr. Humphrey Salwey. 



10. The intaglio of fig. 6, showing the spine. 



IL Pt. Mitchelli? a very large but obscure specimen. Perthshire. Rev. Hugh 

 Mitchell. 



