21 CTENOPTYCHIUS SERRATUS. View of average-sized tooth, on inner aspect (the transverse folds at base of 

 crown broken off). 



21 a Portion of crown and cutting edge magnified, shewing a serration of the denticulations. 



22 Smaller specimen, natural size, front view. 



22 a Portion of ditto magnified, shewing the variety with smooth lobes to the cutting edge. 



23 Large specimen, inner view, from the black beds over the main limestone of Derbyshire ; root perfect in depth, 



but imperfect at the sides. 



24 COCHLIODUS ACUTUS. Right posterior tooth, natural size, Armagh ; seen from above. 

 24 a Profile of same specimen ; seen from the outer or convoluted side. 



24 b Transverse section of No. 24. 



25 Larger and more sharply marked specimen. 



25 a Profile of last specimen (convolution of the margin concealed by the matrix). 



26 Anterior tooth, natural size ; viewed from above. 



27 COCHLIODUS STRIATUS. Natural size, terminal tooth, viewed from above; from the carboniferous limestone 



of Armagh. 

 27 a Portion of surface of ditto, magnified. 



27 b Sketch of smaller perfect specimen (in collection of Capt. Jones, R. N. M. P.) 



28 COCHLIODUS OBLONGUS (Ag.). Posterior tooth, rough fracture, shewing the vertical succession of the teeth, 



with youno' tooth in situ, magnified one and half diameters ; from carboniferous limestone of Armagh. 



29 PHYSONEBIUS ARCUATUS (JPCoy). Large specimen, shewing the perfect base, natural size; from the 



limestone of Armagh . 

 29 a —— Portion of surface, magnified. 



29 b One of posterior teeth, magnified. 



30 PHYSONEMUS SUBTERES. Fragment, natural size ; from carboniferous limestone of Armagh. 



30 a — — Portion of surface, magnified. 



31 CTENACANTHUS CRENATUS. Fragment, natural size ; from the carboniferous limestone of Armagh. 

 3] a • Ditto, section. 



31 b Portion of surface, magnified. 



32 CTENACANTHUS HETEROGYRUS. Fragment of base, natural size, (carboniferous limestone of Armagh,) 



shewing part of the base of insertion and commencement of ridging, with few tubercles. 



33 — ^— Ditto, fragment near middle, shewing the irregular character of the ridging and tuberculation. 

 33 a Portion of surface of last specimen, magnified. 



33 b Ditto, section shewing the broad ridge of anterior face. 



34 CYATHOPSIS ERUCA (IPCoy). Natural size; carboniferous limestone of Bcith. 

 34 a Ditto, vertical section. 



34 b Horizontal section, slightly magnified. 



35 CANINIA SUB-IBICINA (M'Coy). Natural size ; from the carboniferous limestone of Kendal. 



35 a Ditto, vertical section. 



36 DITHYROCARIS LATERALIS (JPCoy). Tail, natural size; from the black beds over tlie main limestone of 



Derbyshire. 



37 MURCHISONIA DISPAR (M^Coy). Natural size, from the carboniferous limestone of Lowick. 



37 a Portion of ditto, magnified. 



38 PLEUROTOMARIA EROSA (M'Coy). Magnified lialf a diameter, under side; from carboniferous limestone of 



Lowick. 



39 Ditto, profile, natural size. 



39 a Ditto, seen from above. 



39 b Ditto, magnified half a diameter. 



40 MACROCHILUS LIMN^IFORMIS (M'Coy). Natural size; from the carboniferous limestone of Lowick. 



41 CARDIOMORPHA ORBICULARIS (M'Coy). From the carboniferous limestone of Derbyshire. 

 41 a Ditto, seen from behind, to shew the inflected dorsal margins. 



