EXPLANATION OF PLATE 3. K. 



jjoTj, The fish-teeth have not been reversed in drawing, so that the terms right and left used in the text apply 



to the specimens, but must be reversed for the drawings. 



1 GLOSSODOS MARGINATUS (^PCoy). Natural size; from the carboniferous limestone of Armagh. 



1 a Ditto, magnified. 



2 POL YRHIZODUS ? PUSILLUS (M^Coy). Natural size, front view; from the carboniferous limestone 



of Armagh. 



2 a Ditto, magnified two diameters. 



2 h Ditto, section and end view, magnified two diameters. 



S CHOMATODUS (HELODUS) OBLIQUUS (M'=Coy). Natural size, front view ; from the carboni- 

 ferous limestone of Armagh. 



4 HELODUS RUDIS (M'^Coy). Natural size, shewing the upper surface and part of margin. 



4 a Portion of surface, magnified. 



5 CLADODUS L^VIS (ISLCoy). Average-sized tooth, natural size ; from the carboniferous limestone 



of Armagh ; middle cusp worn ; lateral cusps broken at apex. 



6 POLYRHIZODUS MAGNUS (M'^Coy). Average-sized tooth, front view, natural size; from the car- 



boniferous Umestone of Armagh. 



7 Ditto, section and perspective end view, natural size, shewing the much lower level of the ridge 



defining the base of the crown on the posterior than on the anterior base. 



8 Ditto, portion of entire width of crown from cutting edge to base, magnified three diameters. 



9 CHOMATODUS (HELODUS) DENTICULATUS (M'=Coy). Side view, natural size (the extre- 



mities broken) ; from the carboniferous limestone of Armagh. 



9 a Ditto, seen from above. 



10 CHOMATODUS CLAVATUS (M'^Coy). Front view of average tooth (slightly imperfect on one 



side) ; from the carboniferous limestone of Armagh. 

 10 a Ditto, profile, shewing the coronal ridge at a low level on the posterior side. 



10 5 Ditto, portion of crown, magnified. 



11 PRISTICLADODUS GOUGHI (M'^Coy). Front view, natural size ; from the carboniferous sandstone 



of Kettlewel, Kendall (apices of the cusps slightly imperfect). 



12 OSTEOPLAX EROSUS (M-'Coy). Portion of one of the plates, natural size; from the lower carboni- 



ferous shales of Cultra, Holywood, county Down. 



12 a Ditto, portion of surface, magnified. 



13 GYRACANTHUS OBLIQUUS (M-^Coy). Spine, natural size, side view, shewing part of the ba.se 



of insertion, but broken at each end ; from the yellow sandstone shale, Moyheeland, Draperstown. 



13 a Ditto, section, a little above the middle. 



14 Ditto, terminal portion, natural size, shewing the comparative smoothness of the ridges towards the 



apex, and the presence in that part of the posterior rows of denticles. 



14 a Ditto, portion of anterior face, magnified. 



15 CTENACANTHUS DISTENS (M'^Coy). Dorsal spine, natural size, imperfect at the tip, shewing 



the elongate tapering base of insertion, and internal cavdty in lower part ; from carboniferous limestone 



of Armagh. 

 15 a Ditto, portion of surface magnified, shewing the variable width and mode of tuberculation of the 



ridges. 



