EDMONDIA OBLONGA. 299 



raised, the beaks being twisted forwards and inwards, contiguous, and situated in 

 the anterior quarter of the shell. Lunule and escutcheon absent. The valves are 

 regularly and convexly swollen, but in very large specimens there is an obscure 

 approach to angulation along the line where the shell becomes compressed to form 

 the posterior slope. 



Interior. — The anterior adductor muscle-scar is large, shallow, and round, and 

 is situated within the antero-superior angle of the valve, encroaching largely 

 upon the umbonal hollow; the posterior is large and rounded, shallow, situated on 

 the hollow of the dorsal slope, remote from the margin. Above this and at the 

 extreme end of the hinge-plate, and just within the margin of the valve, is a small 

 round scar for an accessory muscle. The pallial line is entire and very remote 

 from the margin. The hinge consists of a plate thickened on its external border, 

 which is placed at right angles to the valve, and formed by the valve being bent 

 acutely on itself. This leaves, in casts, two parallel grooves, which become shallower 

 as they pass backwards, and terminate at some distance from the posterior end. 

 The hinge-plate is apparently edentulous. The internal surface as seen in casts 

 shows numerous concentric ridges and sulci, which become broader and further 

 apart as they approach the lower margin. 



Exterior. — The surface is ornamented with bundles of fine concentric strias, 

 separated into groups by well-marked concentric folds and ridges, which are 

 broader near the lower margin. 



Dimensions. — PI. XXIX, fig. 5, the type of Sanguinolaria oblonga, Portlock, 

 measures — 



Antero-posteriorly . . . .56 mm. 



Dorso-veutrally . . . .38 mm. 



Elevation of valve . . . .15 mm. 



Locality. — England : in one of the beds of limestone, Lowick ; the Coombs 

 limestone, Redesdale, Northumberland. Wales : below the Farewell Rock of 

 Glan Rhymney and Beaufort, South Wales. Scotland : the Lower Limestone series 

 of Beith, Ayrshire. Ireland : in black limestone, Errigle Keerogue, co. Tyrone. 



Observations. — When M'Coy described his new species of E. oblonga he was 

 aware of the close similarity of his shell to that described by Portlock. He states 

 {op. sup. cit., p. 501), " The Sanguinolaria oblonga, Portlock, . . . seems to be more 

 compressed, to have a more defined posterior slope, and to have large regular 

 imbrications in addition to the small concentric markings. They may, however, 

 be identical." 



A close comparison of the types of each author, which I am fortunately able 

 to figure through the kind permission of Sir A. Geikie and Professor McKenny 

 Hughes, shows the identity of Sanguinolaria oblonga, Portlock, PI. XXIX, fig. 5, 

 with Edmondia oblonga, M'Coy, PI. XXIX, fig. 1, the differences noted by M'Coy 



