LAMELLIBRANCHIATA. ] UPPER PAL-EOZOIC MOLLUSCA. 509 
ribs parallel with the margin (about four in the space of two lines on all parts of the shell), those abruptly 
disappear on reaching the edge of the posterior slope, and unite on the anterior edge in front of the sinus, 
in parcels of two or three, to form a row of SHOE thick wrinkles on that part. Length one inch five lines; 
Dgqpentions! width from beak to ventral margin =, length of hinge-line from beak about ;%,, width of posterior 
end about =, greatest depth of both valves =. 
It differs from the Hdmondia sulcata (Phill. sp.) in its extremely thin shell, short inflated form, want 
of the thick internal cardinal ridges, the more regular sharp ribs on the sides, and their uniting into large 
wrinkles on the anterior instead of the posterior end. The sulcus bisecting the posterior slope must not be 
supposed to indicate a ridge, as it is a mere linear indentation of the shell. 
Position and Locality—Common in the carboniferous shales of Craige, near Kilmarnock ; carboniferous 
shales near Glasgow ; in the shale-beds at Lowick, Northumberland. 
Explanation of Figures—Pl. 3. F. fig. 5, left valve natural size from carboniferous shales of Craige, 
near Kilmarnock ; fig. 5a, seen from the back, shewing the anterior and posterior lunettes or cartilage supports, 
and the small mesial sulcus of the posterior slope. 
Genus. CARDIOMORPHA (de Kon.) 
Gen. Char.—Shell very thin, equivalve, inequilateral; margins closed; obliquely, very tumid; beaks very 
tumid, produced, spirally inrolled to the anterior side; no hinge-teeth; hinge-margin inflected nearly at right 
angles to form a hollow lunette, running from the beak nearly to the anal cardinal angle; two adductor 
impressions in each valve; pallial scar simple, very faintly marked; a shallow anterior depression beneath the 
beaks, but the margin sharp and prominent. 
Resembling the recent /socardia exactly in form, but perfectly distinguished by the want of teeth, which 
character, and the inflection of the cardinal margin, approximates the genus to the Leptodomi (M*Coy), from 
which they differ by their large inrolled beaks, and closed margins, without byssal furrow, &c. From the ex- 
treme thinness of the shell the muscular and pallial scars are rarely visible. 
CARDIOMORPHA ? MODIOLIFORMIS (A7nq). 
ftef—King, Perm. Foss. t. 14. f. 18 to 23. 
Desc.—Oblong, extremely gibbous diagonally from the beaks to the respiratory angle, from which line the 
valves slope rather abruptly and flatly to the dorsal and yentral margins; beaks very large, obliquely incurved 
over the anterior end; anterior end forming an obtuse lobe, searcely or not at all projecting in front of the 
beak, having a deep semicordate Repco beneath the beak in each valve; ventral margin nearly straight, 
usually al a shallow byssal sinus a little in front of the middle, from which when it exists a shallow concavity 
extends obliquely forwards towards the beak; posterior end obliquely subtruncate ; the respiratory angle obtusely 
rounded ; hinge-line slightly elevated, shorter than the shell, inflected; cartilage margin rather broad, the angle 
of inflection forming a strong ridge; posterior slope flattened or slightly concave. Surface marked with coarse, 
close, obtuse, unequal lines of growth, usually crossed on the posterior and ventral portion, by rather distant, 
obscure, narrow, radiating lines, elevated near the beak, but becoming impressed towards the margin of old 
specimens ; separated by flat spaces about half a line wide at three or four lines from the beak; about three 
times wider than the ridges. Average length six inches, proportional width (greatest at middle of length) ;%;, 
depth of one valve (greatest a little in front of the middle) 4. Casts shew the sulcus of a clavicular ridge 
behind the anterior adductor. 
The obscure radiating ridges do not constantly appear, and are seldom seen close to the beak. The distinct- 
ness of the anterior addheton ad its bounding ridge, as well as the occasionally well-marked byssal sinus, would 
incline me to place this species in Sanguinolites nates than in Cardiomorpha. 
Position and Locality—Not uncommon in the Permian limestone of Humbleton. 
