Vol. 6S.'] LOWEE CARBONIFEROTJS EISHES. 573 



in its anterior half. Antero-lateral half of the coronal face 

 raised into a prominent round ridge, which is partly subdivided 

 by transverse constrictions into a few large rounded bosses ; 

 postero-lateral half flattened, curving a little upwards at the 

 postero-lateral border. 



Remarks. — This species is known only by two satisfactorily 

 preserved ' upper ' dental plates and a few fragments. The type- 

 specimen (B.M. P 10335) measures 12 mm. in width at its inner 

 border, while the second specimen is somewhat larger. In the 

 former five distinct bosses are seen on the rounded antero-lateral 

 ridge, and there would probably be a sixth at the apex, which is 

 broken away. In both cases the coronal face is much abraded, so 

 that the punctations of the dentine, below the original surface, are 

 conspicuous ; but in the larger specimen there are still traces of 

 sigmoid ally- curved lines extending from the grooves between the 

 antero-lateral border : these suggest that the dental plate results 

 from the fusion of ffelodus-ahnYied teeth in which the coronal 

 eminence occupied the anterior half. 



D. ganucodi, which is named after its discoverer, differs from 

 all other known species of the genus in the coarse beading of the 

 antero-lateral eminence of its dental plate, the relative evenness 

 of its postero-lateral half, and the slightness of its curvature. A 

 fragment from the St. Louis Limestone of Illinois, which has been 

 referred to D. intermedins,^ perhaps approaches it most closely. 



Horizon and localities. — Solenopora Sub-zone. ArcJioeo- 

 cidaris Bed, Shap Abbey, Shap ; and Vaughania-cleistoporoides 

 Band, Stone Gill, liavenstonedale. 



OocHLioDus viEGATUs, sp. uov. (PL LII, figs. 4 a & 4 6.) 



Specific characters. — Anterior dental plate scalene-tri- 

 angular in shape ; its sharp oblique coronal ridge divides the 

 surface into two equal areas, of which the postero-lateral is smooth 

 and slopes gradually downwards to the border, while the antero- 

 lateral is strongly ridged, with a tendency to the branching of at 

 least one ridge. Postero-lateral border slightly crimped. 



Hemarks. — The anterior dental plate of (7oc7i?zocZi<5 often exhibits 

 a tendency to bear radiating ridges on its antero-lateral extensions, 

 but the new tooth is unique in the strength of this ridging. The 

 specimen described also differs from all other known teeth of 

 Coohliodus ; but it resembles Psepliodus, in the crimping of at least 

 part of the border. 



Horizon and locality. — Vaugliania-cleistoporoides Band, 

 Solenojwra Sub-zone. Stone Gill, Ravenstonedale. 



' A. H. Worthen & 0. St. John, G-eol. Surv. Illinois, toI. yiI, Geol. & Pal, 

 (1883) pi. ix, fig. 15. 



