PLATE VI. 



1 . Pteraspis rostrcdus, Ag. A very fine specimen ; with the surface markings (striae 



and pits) well shown. Cradley. Dr. Grindrod. 



2. A similar specimen, showing more of the posterior portion of the shield. Cradley 



Dr. Grindrod. 



3. A natural cast of the surface of part of the shield of Pt. rostratus, showing the 



disposition of the markings round the orbit and on the cornu. Notice in this 

 and in fig. 1 the aperture {a) in the cornu, giving the appearance of a detached 

 projecting angle to part of the cornu. Author's cabinet. 



4. A disc of Pt. CroticMi, showing clearly the characteristic form and the deep 



incision posteriorly for the spine. 



5. Cyathaspis Syniondsi. Cornstones, Herefordshire. In the Museum of the Geolo- 



gical Survey (Jermyn Street). 



6. A specimen of Pt. rostratus, showing the superficial markings of the posterior 



portion of the shield. In the collection of Mr. James R. Gregory. 



7. 8. Rostra of Pteraspis Crouchii. From the neighbourhood of Ludlow. 

 9. A fragment of Pt. rostratus, consisting of the ' orbital portion.' 



