LAMELLIBRANCHIATA. | UPPER PAL/ZKOZOIC MOLLUSCA. 499 
PINNA FLEXICosTATA (Af‘Coy). Pl. 3. E. fig. 11, 12, 13. 
Ref —M Coy, Syn. Carb. Foss. Irel. t. 19. f. 1. 
Desc.—Triangular, nearly three times longer than wide, very gibbous along the middle; section elliptical, 
the ventral third of each valve free of ribs its entire length, and crossed obliquely by large wrinkles or undula- 
tions of growth, which become nearly obsolete on the ridged portion of the shell; beak smooth for six or seven 
lines, beyond which the middle and dorsal thirds of the surface are covered with strong unequal ridges, separated 
by rather narrower, deep, concave sulci, straight and nearly simple along the dorsal third, occasionally inter- 
rupted and more flexuous along the middle third, where several of them are also divided by a small intervening 
sulcus, (at two and half inches from the beak, about seven ridges in half an inch). Average length about three 
inches, proportional greatest width at posterior end ;;, depth of both valves in the middle 3. 
This is a much smaller and more gibbous species than the P. flabelliformis, it has smaller and more 
flexuous ridges, and is particularly distinguished by the ventral third of the whole length of each valve being 
free of longitudinal ridges. 
Position and Locality—Very common in the impure carboniferous limestone of Lowick, Northumberland ; 
very common in the red millstone-grit of Honey-Pen Hill; in the red carboniferous grit of Brandon Hill. 
Explanation of Figures —P1. 3. E. fig. 11, left valve, natural size, from Lowick; fig. 12, right valve ; 
fig. 18, section of both valves. 
PINNA SPATULA (M°Coy). PI. 3. E. fig. 9 and 10. 
Ref.—M°Coy, Ann. Nat. Hist. 2nd Series, Vol. XII. 
Desc.—V alves very narrow and much elongated, about four times longer than the width of posterior end, 
very slightly convex except at the beaks, which are pointed and almost cylindrical ; the sides gradually flattening 
as they approach the posterior end, which is subtruncate or slightly rounded obliquely ; cardinal margin slightly 
thickened, with the cartilage ridge very close within its edge; surface perfectly smooth, or with very faint 
laminar lines of growth parallel with the margins. Length of large rather imperfect specimen five and half 
inches, proportional greatest width at posterior end about = ; greatest depth *, or =. 
Fragments of this species might be taken for a So/en, and the S. siliquoides (Kon.) may have some affinity 
with it, though specifically distinguished. The muscular impression is rather large, though superficial, quadrato- 
reniform rather behind the middle of the length, and nearer to the cardinal than the ventral margin. 
Position and Locality.—Specimens of the above large size rare in the carboniferous limestone of Derby- 
shire; specimens about three inches long, and slightly more convex, in the carboniferous limestone of Lowick. 
Explanation of Figures ——P1. 3. E. fig. 9, left valve, natural size, from the carboniferous limestone of 
Derbyshire; fig. 9 a, section near anterior end; fig. 9 6, profile, near posterior end; fig. 10, smaller and more 
perfect specimen from Lowick, Northumberland. 
Genus. EDMONDIA (de Koninck). 
Gen. Char.—Shell equivalve, inequilateral, tumid, short, oblong or rounded, closed all round; dorsal and 
ventral margins slightly convex ; beaks tumid, with an impressed lunette beneath them; surface with concentric 
strize or wrinkles ; no teeth, but an internal lamellar cartilage support, which is much dilated within the cavity 
of the beaks, the broad end forming the slits in casts coinciding with the edges of the anterior lunette, and the 
posterior end running nearly parallel to and close within the hinge-line; dorsal margins erect and simple ; two 
simple adductor impressions, often with an accessory impression over each; pallial scar simple, entire. 
The remarkable state of preservation of the Lowick fossils in the Cambridge collection enabled me to detect 
the characters of the muscular and pallial impressions, and to demonstrate, by the integrity of the latter, that 
the genus has no affinity to the Mactridw, as M. de Koninck supposed; and instead of belonging to that family 
it is clearly referrible to a different and lower order. The genus is closely allied in appearance to the short species 
of Sanguinolites, but differs by the dorsal margins being erect and compressed, instead of inflected to form a 
hollow lunette for the external cartilage, and the margins being closed. 
