16 CTENAOANTHUS DENTICULATUS (M'=Coy). Dorsal spine, natural size; from the yellow sand- 

 stone-shale of Monaduff. 



16 a Ditto, some of the ridges near the anterior face, magnified. 



17 DIPRIACANTHUS. New species. Dorsal spine, natural size (base broken off); from the carboniferous 



limestone of Armagh. 

 IS DIPRIACANTHUS STOKESII (M°Coy). Natural size; from the carboniferous limestone of Armagh. 



18 a Ditto, portion magnified. 



19 HOM ACANTHUS MICRODUS (M'Coy). Dorsal spine, imperfect at each end, natural size; from 



the carboniferous limestone of Armagh. 

 19a Ditto, portion, magnified. 



20 HOMACANTHUS MACRODUS (M^Coy). Dorsal spine, natural size ; from the carboniferous hme- 



stone of Armagh. 



20 a Ditto, portion, magnified. 



21 HOMACANTHUS. Natural size ; from the carboniferous limestone of Armagh. 



22 ASTEROPTYCHIUS SEMIORNATUS (M-^Coy). Portion of spine, imperfect at each end; from 



the carboniferous limestone of Armagh. 



22 a Ditto, portion of surface magnified, shewing the single row of tubercles. 



23 ASTEROPTYCHIUS ORNATUS (Ag. name only). Portion of spine near base, imperfect at each 



end, natural size ; from the carboniferous limestone of Armagh. 

 2.3 a Ditto, section near base. 



24 Ditto, more near the distal end. 



2i a Ditto, portion of surface, magnified. 



2.5 PHYSONEMUS ARCUATUS (MCoy). Fragment of spine, natural size; from the carboniferous 



limestone of Armagh. 

 2.3 a Ditto, portion of surface, magnified. 



26 ERISMACANTHUS JONESII (M'^Coy). Dorsal spine, shewing the posterior spine, imperfect at the 



apex, and the anterior prop -like branch denuded of some of its tubercles ; the base of insertion also 

 absent. 



27 Ditto, dotted outline shewing the perfect form (from the collection of Captain Jones, R. N. M. P.), 



shewing the base of insertion, anterior and posterior branches, and denticulation of the latter. 



27 a Ditto, compressed section of base of anterior branch. 



27 5 Ditto, portion of anterior branch with the tuberculation perfect. 



27 c Ditto, depressed section of extremity of anterior branch. 



27 (I Section of posterior spine, natural size. 



