EXPLANATION OF PLATE 3. G. 



1 CENTRODUS STRIATULUS (M'=Coy). Perfect tooth, natural size, on lower corner of matrix. On 

 upper end a rough section of a smaller tooth shews the great size of the pulp-cavity and its width at 

 base. From the carboniferous shale of Carluke. 



1 a Magnified view of the lower tooth of fig. 1 . 



1 h Section of base of last specimen, shewing the great size there of the pulp-cavity. 



1 c Section of ditto, at one-third the length from the apex. 



1 d Portion of last section, highly magnified, as a transparent object, shewing portion of central pulp- 



cavity, the dentine tubes, calcigerous cells, and ? enamel layer of surface. 



2 PEISTICLADODUS DENTATUS (M^Coy). Tooth, natural size, outer surface; from the black 



limestone beds of Derbyshire. 



2 a Base of ditto, on the inner side, seen from above. 



3 Profile of another specimen. 



4 PETALODUS ACUMINATUS (Ag.) Inner aspect of tooth, natural size ; from the carboniferous 



limestone of Derbyshire. 



4 c Outer side of same tooth. 



5 CLIMAXODUS IMBRICATUS (M<=Coy). Natural size, from the carboniferous limestone of Derby- 



shire. 



5 a Portion of surface of ditto, magnified. 



6 PETRODUS PATELLIFORMIS (M«Coy). Single perfect tooth, viewed in profile, natural size, from 



the carboniferous limestone of Derbyshire. 

 6 a Ditto, magnified. 



6 I Vertical section, from grinding surface to base, highly magnified, shewing the numerous irregularly 



branching medullary canals, giving off dentine tubes at right angles, and the superficial coat of dense 

 ganoine, without canals. 



7 Tooth, natural size, seen from above, the apex worn down by use. 



8 Tooth, natural size, under side of base. 



9 CHIRODUS PES-RANiE (M'Coy). Natural size, from the carboniferous limestone of Derbyshire. 

 9 a Ditto, magnified. 



10 PCECILODUS ALIFORMIS (M-'Coy, upper figure). Natural size, from the carboniferous limestone 

 of Derbyshire. 



10 AOROLEPIS HOPKINSI (M'Coy, lower figure). Fragments of two scales, natural size, from the 



carboniferous limestone of Derbyshire. 



11 PCECILODUS FOVEOLATUS (M-^Coy). Natural size, from the carboniferous limestone of Derby- 



shire. 



12 PSAMMODUS CANALICULATUS (M'-Coy). From the carboniferous limestone of Armagh ; tooth. 



natural size. 



13 LEPTACANTHUS JUNCEUS (M<^Coy). Fragment of fin-ray, natural size, from the carboniferous 



limestone of Derbyshire. 



13 « Portion of ditto, magnified. 



14 LEPTACANTHUS JENKINSONI (M'Coy). Portion of ray, natural size, imperfect at each end. 



shewing the anterior keel and some of the posterior denticles, and the interruption of the ridges above. 



14 a Small portion of surface magnified, shewing the occasional interruption of the ridges, and the inter- 



vening punctured striae. 



1 5 do. portion nearer to the distal extremity, natural size. 



15 « Portion magnified from near the apex, shewing the form of section, &c. 



] 6 Fragment, natural size, from nearer the apex. 



17 RHIZODUS GRACILIS (M'^Coy). Dentary bone and teeth, natural size, (wanting a little of the pos- 

 terior end). The letters a, 5, and c mark the apparent places of the posterior laniary teeth. From 

 the carboniferous shales of Gilmerton. 



