PLATE XIII. 



Fig. 



1. Didymaspis Grindrodii. The shield is imbedded with its concave surface upwards. Dr. Grindrod's 



collection. 



2. Natural cast of the same. From the red micaceous beds above the Auchenaspis Grits of Ledbury. 



The artist has not fairly represented the character of these specimens, which are better seen in 

 vol. iv of the ' Geological Magazine,' pi. viii, figs. 4 and 5. 



3. Auchenaspis Egertoni. 

 4. 



Aa. A part of fig. 4 enlarged, showing the orbits, antorbital fossae and their septum, the superficial 

 lamina which covers them in having been broken away, and the hexagonal areolation of 

 the material of the test, Tiie surface is not preserved ; it is tuberculated, as in Cephalaspis. 

 ."). A part of fig. 4 enlarged. The difference in form and size of the cornua in these specimens is due to 

 the more or less covering by matrix, a condition which the artist has not rendered apparent 

 in these or the other figures. 



3, 4, and 5 are from the Auchenaspis Grits (Passage-beds), Ledbury, and belong to Dr. Grindrod. 

 6,6b. Fragments of scales from beds at the base of the Cornstones, Ledbury. Dr. Grindrod. 

 7, 8. Auchenaspis Salteri. The Passage-beds near Ludlow. Mr. Lightbody. 



!) — 14. Eukei-aspis {Auchenaspis?) pustuJiferus, from the Downton Sandstone of Ludford Lane, near 

 Ludlow. 



9. Central part of the head-shield, showing the orbits and finely tuberculated ornament in intaglio. 

 The margin is fractured, and has not the regularity here given by Mr. Lightbody. 



10. Fragment, showing the central part of the shield, enlarged. Dr. Grindrod. 

 10a. The tubercular ornament still more enlarged. 



1 1 . One of the long cornua, showing the denticulations on the outer margin which led to such spe- 



cimens being considered as the jaw of a fish, the Plectrodus pustuliferus of Siluria. Mr. 

 Lightbody. 



12. A specimen showing the marginal cavities or cells exposed by the breaking away of the upper 



surface of the shield. Dr. Grindrod. 



13. A specimen which shows well the form of the shield and cornua (see woodcut, fig. 31). The 



whole of the superficial lamina of the test is gone, and the subjacent cavities and laminae 

 exposed. The part here preserved appears to agree with the anterior moiety of a shield of 

 Auchenaspis or Didi/maspis. The two bodies which have the appearance of orbits are cavi- 

 ties nnderlying the shield surface, like the marginal cells. The true orbits lie anteriorly to 

 this. Compare the figure of these genera. Mr. Lightbody. 



14. A fragment which shows beautifully the impression of one of the long cornua and a part of the 



head. The denticulations of the margin are not drawn finely enough, and the cornu is 

 represented as thicker than it is really. Mr. Lightbody. 

 15, 16. Fragments, the like of which are not uncommon in the lower parts of the Cornstones of Here- 

 fordshire, probably the angles or cornua of Ceplialaspidian shields which have been rolled and 

 washed. Dr. Grindrod. 



17, 18. Mesially placed scutes belonging to some Cephalaspid of the same character and mode of 

 occurrence as figs. In and 16. A specimen of very much larger size, similar to fig. 17, has come 

 under my notice, and appeared to belong to Zenaspis. It is not figured in this work. Compare 

 PI. VIII, figs. 2, 3, and 4, with these. Dr. Grindrod. 



19. Cephalaspis Li(/hthodii, from the Passage-beds near Ludlow; the under surface of a very large and 



characteristic marginal rim is presented ; in the lower part of the specimen a portion of perhaps 

 the dome of the shield is seen in intaglio ; more probably this belonged to an additional scute. 

 Mr. Lightbody. 

 19rt. A part of the tubercular ornament enlarged. 



20. Kallostrakon podura. Lower Cornstones, Herefordshire. Dr. Grindrod. 



2'. Intaglio of a similar fragment, differing a little iu the character of its markings. Dr. Grindrod. 



