PLATE I. 



Fig. Page. 



Agnostus agnostiformis (M'Coy). 3. 



1. Outline restoration of head-shield and pygidium, after Salter, ' Mem. G-eol. 

 Surv.,' dec. xi, pi. i, figs. 8 a, 10 a. 



Agnostus girvanensis, sp. nov. 



Imperfect individual with one thoracic segment in position. X 4. Bal- 



clatchie. Mrs. Gray's' Collection. 

 Pygidium showing median ridge and tubercle on axis. X 3. Balclatchie. 



Museum of Practical Geology. 

 Outline restoration of complete individual. 



Agnostus perrugatus, Barrande. 



5. Nearly perfect head-shield. X G. Whitehouse. Mrs. Gray's Collection. 



(Figured by Nicholson and Etheridge, ' Mon. Silur. Foss. Girvan,' 



fasc. hi, pi. xx, fig. G.) 

 G. Impression of head-shield. X 3. Whitehouse. Mrs. Gray's Collection. 

 7. Imperfect pygidium. X 5. Whitehouse. Mrs. Gray's Collection. 



Agnostus tardus, Barrande. 7. 



8. Head-shield. X G. Whitehouse. Mrs. Gray's Collection. 



9. Outline restoration of complete individual, after Barrande (' Syst. Sil. 



Boheme,' vol. i, pi. xlix, fig. 1 h). 



Trinucleus bucklandi, Barrande. 10. 



10. Complete individual, showing genal prolongation of fringe, character of 



pits, etc. X 2. Drummuck. Mrs. Gray's Collection. 

 10a. Side view of same. 



11. Head-shield, showing projection of glabella, lateral pits, tubercle and 



bending down of fringe. X 2. Drummuck. Mrs. Gray's Collection. 

 11a. Side vieAV of same, showing radial arrangement of pits and groove in 

 fringe where shell is removed. 



12. Side view of head-shield, showing genal portion of fringe and spine with 



shell preserved, as in fig. 10 a. X 2. Drummuck. Museum of 

 Practical Geology. 



13. Head-shield with fringe wanting, showing minute pitting on cast where 



shell is removed. X 1^. Drummuck. Museum of Practical Geo- 

 Jogy. 



14. Pygidium, showing paired pits between rings on axis. X 3. Drum- 



muck. Museum of Practical Geology. 



