414 CARBONIFEROUS LAMELLIBRANCHIATA. 



very feebly swollen. The anterior end is short, but the deepest part of the shell 

 from above downwards, closed, its border rounded. The inferior margin is long 

 and gently convex ; the posterior narrow and bluntly curved, the hinge-line long, 

 and almost straight. The umbones are small, very inconspicuous, and placed very 

 far forwards, but not terminal. Passing backwards and downwards from the umbo 

 to the postero- inferior angle is an oblique, more or less well-marked rounded ridge, 

 which separates the long narrow dorsal slope from the rest of the valve, which 

 does not show any sulcation. 



Interior. — The anterior adductor scar is small, and placed immediately within 

 the antero-superior angle. The hinge-line seems to have been thickened posteriorly* 

 and to leave a long narrow groove in casts. 



Exterior. — The surface is ornamented with fine lines and strige of growth. 



Dimensions. — PI. LI, fig. 3, the type specimen of M'Coy's Solenopsis minora 

 measures — 



Antero-posteriorly . . . .25 mm. 



Dorso-ventrally . . . .7 mm. 



A large specimen from the Knife Scar Limestone north of Shap, PI. LI, 

 fig. 4, measures — 



Antero-posteriorly (probably incomplete) . . 53 mm. 



Dorso-ventrally . . . .15 mm. 



Localities. — England : quarry in the Knife Scar Limestone a mile north 

 of Shap village, Westmoreland; Carboniferous Limestone of Thorp Cloud, 

 Derbyshire. Ireland: in gritty Limestone, Clogher; Drurareagh ; Dungannou; 

 CO. Tyrone; Ballydufi", river Bunnow, King's Co. 



Observations. — The type of M'Coy's Solenopsis minor, PL LI, fig. 3, is pre- 

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

 refigure the specimen, which consists of a right valve, a little imperfect at the 

 antero-inferior angle. The type of Portlock's Solen pelagicus is in the Jermyn 

 Street Museum, PL LI, fig. 5. 



Most authors have considered M'Coy's shell to be identical with S. pelagicus, 

 Groldfuss, but this is a much larger shell with a strong angular oblique ridge, and 

 a well-marked sulcus from the umbo to the inferior border ; moreover it occurs in 

 beds of Devonian age. 



De Koninck discusses the question of the locality of Goldfuss's type, pointing 

 out that in 1832 Ratigen, near Dusseldorf, and in 1840 Eifel were respectively 

 given as the sources of the specimen by its author ; and he says, " For my part I 

 have no doubt that the example figured by Goldfuss comes from the Carboniferous 

 Limestone of Ratigen, and that the species should be erased from the list of 

 Devonian shells." 



Beushausen (op. cit.) points out that the specimen figured by de Koninck from 



