CONOCARDIUM INFLATUM. 459 



keeled or sliarp, noi- does it correspond with the line of greatest convexity, but is 

 at some distance behind it. Valves curved on themselves from above downwards. 

 A short, thick flange extends from the lower part of the external margin of the 

 posterior surface. 



Interior. — As far as can be seen, exactly like that of G. Herculeum. 



Exterior. — The surface was probably smooth ; but in the condition in which 

 the type specimen exists there are regular, equidistant, radiating ribs, fewer in 

 number aud further apart on the anterior wing. Shell thick, composed of several 

 layers, the intermediate ones composed of cellular ribs. 



Dimensions. — PI. LI, fig. 14, the type of M'Coy's PleurorhyncJms mflatns, 

 measures — 



Antero-posteriorly (estimated; type incomplete in front) . 20 mm. 



Dorso-ventrally . . . . .16 mm. 



From side to side . . . . .16 mm. 



Localities. — England : the Carboniferous Limestone of Derbyshire ; "Withgill ; 

 Hill Stebden, Hill Bolton, Yorkshire. Ireland : the Carboniferous Limestone of 

 Carrickboy, Longford, and Claines ; Doohybeg and Ragreah, co. Limerick, 

 Scotland : the Lower Limestone series of Corrieburn, near Kilsyth. 



Observations. — The type of this species is preserved in the Griffith Collection 

 in the Royal Museum of Science and Art, Dublin ; and I am permitted to 

 refigure it by the kindness of the authorities. It is quite possible that this 

 species is only a variety of C. aliforme, which it closely resembles; but the 

 following differences are noticeable : it is comparatively more gibbose and 

 transverse ; the posterior surface is more oblique, less flattened, and concave ; the 

 body of the valve is less suddenly bent and adpressed to form the posterior 

 surface. The type has unfortunately lost the greater part of its anterior end and 

 its rostrum. I have been able to find very few specimens which can be referred 

 to G. inflatmn. Three specimens from Irish localities are, however, in the 

 Woodwardian Museum, which also possesses a specimen labelled Derbyshire, 

 which should, I think, be referred to this species ; and I have also collected a few 

 specimens from the Yorkshire localities noted above, which possess the peculiar 

 characters of G. iiiflatum to which I have drawn attention above. 



De Koninck recognises the presence of C. inflatum in Belgium, at Anseremme, 

 Etage II, and separates the species from C. aliforme " par sa forme plus allongee, 

 son extremite anterieure plus obliquement tronquee, et son rostra plus gi'ele." 



G. eximium and G. intermedium of de Koninck seem to be not unlike the 

 species under discussion. 



