PLATE XX. 



Pia. Page. 



Phacops (Chasmops) bisseti, sp. nov. 157. 



1. Complete individual, x lj. Lady Burn. Mr. Bisset's Collection. (Pygidium fore- 



shortened owing to curvature of body.) 

 la. Side view of same specimen, x 1L 

 1/'. Pygidium of same specimen, x 2. 



2. Head-shield of same specimen from wax mould, x 2. 



3. Head-shield of another specimen, x 2.1. Thraive Glen. Mrs. Gray's Collection. 



Asaphus (Isotelus) instabilis, Reed. 162. 



4. Free cheek. X 2|. Dow Hill. Mrs. Gray's Collection. 



Cyclopyge cf. gigantea (Barrande). 163. 



5. Pygidium. x 3. Whitehouse Bay. Mrs. Gray's Collection. 



Ampyx incurvus, sp. nov. 161. 



6. Impression of side of head-shield, showing curved frontal spine. X 4. Dow Hill. 



Mrs. Gray's Collection. 



7. Head-shield, showing the lateral scars on glabella, x 2\. Ardmillan. Same Collection. 



8. Ditto, with several thoracic segments attached, x 3. Dow Hill. Same Collection. 



Illaenus memorabilis, sp. nov. 165. 



9. Middle portion of head-shield, x 2. Dow Hill. Mrs. Gray's Collection. 



Illaenus bowmani, Salter. 164. 



10. Hypostome attached to head-shield of complete individual, x 2. Starfish Bed, Thraive 



Glen. Mrs. Gray's Collection. 



Illaenus balclatchiensis, Reed ?. 163. 



11. Hypostome. x 3. Balclatchie. Mrs. Gray's Collection. 



Lichas (Platylichas) grayi, Fletcher, var. 167. 



12. Head-shield, x 2! 2 . Mulloch Hill. Mrs. Gray's Collection. 



