SCALDIA BENEDENIANA. 337 



hinge-line, and placed somewhat in front of the middle line of the valve. The 

 shell is regularly gibbose, without compression or oblique ridge, nor is the dorsal 

 slope marked off from the rest of the valve. Escutcheon and lunule absent. 



Interior. — The anterior adductor muscle-scar is pear-shaped, and situated in 

 the umbonal hollow remote from the mai'gin, bounded behind by a broad shallow 

 ridge. The posterior adductor scar is shallow, and placed in the hollow of the 

 dorsal slope remote from the margin. Pallial line simple. Hinge not exposed in 

 British examples, but it is known in Belgian specimens to be normal. The cavity 

 of the valve is marked by obscure concentric grooves, especially near the lower 

 margin. 



Exterior. — The surface of the valve is ornamented by well-marked concentric 

 ridges and lines of growth, with here and there deeper broad concentric grooves 

 in which the striaa of growth are still marked. 



Dimensions. — Fig. 1, PI. XXXVII, in the Museum of the Geological Survey, 

 Jermyn Street, measures — 



Antero-posteriorly . . . .21 mm. 



Dorso-ventrally . . . .19-5 mm. 



From side to side . . . .13 mm. 



Localities. — Ireland : the Carboniferous Limestone of Kildare and Tuogh, co. 

 Limerick. 



Observations. — This species was described and figured by de Ryckholt as one 

 of six species belonging to his new genus Scaldia. De Koninck has retained five 

 of these ; but some of them, if not all, are probably slight varieties of the same 

 shell. Added to these should be some of the species described by de Ryckholt 

 under the genus Cardiomorpha, — G. Lacordaireana, G. solida, G. sector, and G. 

 orbitosa. 



It is to be noted that all the species of Scaldia described by de Ryckholt were 

 obtained from the beds of Tournay, while eight of the ten species retained by de 

 Koninck are from the same locality. 



In the well-preserved condition this species is easily distinguished by the 

 well-marked concentric grooves and ridges of its surface, and its suborbicular 

 contour. The surface of S. fragilis, on the contrary, is much more nearly smooth' 

 and it has a somewhat hollowed dorsal slope, and is less oblique. 



Although this species is found in at least two localities in Ireland, I am unable 

 to identify any of the shells figured by M'Coy as belonging to this genus. At 

 present I have not met with the species in the Carboniferous Limestone of 

 England. 



