LAMELLIBRANCHIATA. | UPPER PALAZOZOIC MOLLUSCA. 501 
It is doubtful whether this species be perfectly identical with that of De Koninck, as it is concentrically 
ridged as well as striated ; the proportions however agree, and the species is distinguished from all ages of the 
E. unioniformis by the narrower and much less tumid valves. Casts shew the internal cartilage ridge below the 
erect cardinal edge, as in the other Hdmondic, its broad anterior end coinciding with the edge of the anterior 
lunette. 
Position and Locality —Rare in the impure carboniferous limestone of Lowick, Northumberland. 
EpMonDIA MurcHISONIANA (King). 
ftef—King, Perm. Foss. t. 14. f. 14 to 17. 
Desc.—Oblong, dorsal and ventral margins nearly parallel, and nearly straight ; anterior and posterior ends 
subtruncate, obtusely rounded ; beaks tumid, obliquely incurved, prominent near the anterior end, with a small, 
very deep, wide, cordate lunette beneath them; valves evenly tumid, arching gradually to the ventral and poste- 
rior margins, more abruptly to the anterior, and to the dorsal margins; surface sharply sculptured, with equal, 
very prominent strize, parallel with the margins (averaging ten in one line at two lines from the beak), two or 
three of which, near the edge of old specimens, are more prominent than the rest, and slightly imbricated, 
forming slight wrinkles. Casts shew the thick cartilage plate beneath the anterior part of the dorsal line, dilating 
within the beak to the edge of the anterior lunette. Length five lines, proportional width =, width of posterior 
end *, length of anterior end ;;, depth of one valve ;;. 
According to Prof. King, specimens occur occasionally one inch long; but I have never seen any exceed- 
ing half an inch. It is a beautifully-marked and very distinct species. 
Position and Locality—Rare in the Permian limestone of Humbleton. 
EpMonpIA OBLONGA (J/°Coy). PI. 3. F’. fig. 10. 
Compare Sanguinolaria oblonga Portk. Geol. Rep. t. 36. fig. 2. 
Desc.—Elongate-oblong, tumid, sides slightly flattened ; posterior slope undefined, anterior and posterior 
ends broad, subquadrate, rounded ; dorsal and ventral margins subparallel, nearly straight, slightly convex ; beaks 
large, near the short anterior end, which is abruptly compressed in front of them; lunette beneath the beaks 
small, oval; surface with numerous small, rounded, subequal, concentric wrinkles (about four or five in quarter 
of an inch at the middle of the shell). Length two inches two lines, proportional width from beaks =>, width of 
posterior end ;%, length of anterior end ;;,, depth of both valves ;;. 
Var. 8. brevis, proportional width =. 
In the casts extremely faint indications of oblique, radiating, minute strize are seen, and the cardinal ridge 
is very thick, extending nearly as long as the hinge in each valve, leaving the cardinal edges erect between them; 
also the large anterior and posterior adductors with the simple pallial impression, and traces of a small accessory 
impression over the posterior adductor. In a few specimens the concentric ridges are somewhat larger and less 
regular on the posterior slope. The var. 8. brevis differs in nothing but the shorter figure above given, and I 
haye seen most of the intermediate grades. The Sanguinolaria oblonga Portlock (Geol. Rep. t. 36. f. 2) 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. The so-called /socardia unioniformis (Phil.) 
seems to differ by its narrow posterior end, and wrinkles confined to the posterior slope. The dilated cartilage 
plate within the cavity of the beak of each valve is about two lines wide, being continued as usual from the thick 
ridge below the hinge-margin, and the broad end abutting against the anterior lunette ; it is marked with rather 
strong marginal lines of growth, and very faint, fine, radiating stric. 
Position and Locality.—Abundant in the dark, impure carboniferous limestone of Lowick, Northumberland. 
Explanation of Figures—PI|. 3. F. fig. 10, right valve, natural size, internal cast, shewing the large 
adductor impressions, connected by the simple pallial scar (the thick cartilage plate beneath the simple cardinal 
margin too faintly expressed) ; fig. 10 a, end view to shew the anterior lunette (the indications of the thick 
cartilage plate on each side of the hinge-line too faint). 
