504 BRITISH PALAZOZOIC FOSSILS. ( LAMELLIBRANCHIATA. 
tion confined exclusively to the posterior slope, as he seems to indicate. M. de Koninck’s figure, on the other 
hand, is too nearly orbicular, the anterior end being too long and the ventral margin too much arched to agree 
with the present species; the substance of the shell is most unusually thick in the adult; the internal cast dis- 
playing all the generic characters well. Young specimens eight lines long are not uncommon, retaining all the 
proportions of the adult, and towards their margin the obsolete concentric wrinkles are about six in one line ; 
these also have the depth of both valves a little above =, and not equal to the width, as in De Koninck’s speci- 
men. Specimens in some states of preservation shew faint traces of close, radiating, microscopic striz. 
Position and Locality ——Rare in the limestone of Lowick, Northumberland. 
Family. CAZLONOTID. See p. 275. 
Genus. SANGUINOLITES (d/°Coy). See p. 276. 
SANGUINOLITES CLAVA (J/’Coy). PI. 3. F. fig. 12. 
Ref—MCoy, Ann. Nat. Hist. 2nd Series, Vol. WII. 
Desc—Elongate, clavate or subpyriform; anterior end large, very short, obtusely rounded; dorsal and 
ventral margins with a slight upward curvature, slightly converging to the posterior end, which is slightly 
narrowed, subtruncate, rounded; beaks large, obtuse, a broad-ovate striated lunette beneath them on the 
anterior side; posterior lunette the length of the hinge-line, wide, hollow, bounded by the obtuse ridges 
of the dorsal margins; ventral margin gently convex; valves very convex in front, most so a little behind 
the beaks, half-way between them and the ventral margin, from thence abruptly sloped to the anterior margin, 
and gradually becoming more compressed towards the posterior end; posterior slope gently convex, undefined ; 
diagonal ridge not marked. Surface covered with thick, rugged, subequal ridges, arising a little behind the 
anterior lunette, and slightly thickening towards the posterior slope, where they average three to four in half an 
inch in the middle of the shell; posterior slope obscurely defined by their termination, and only marked by fine 
striee of growth parallel with the end, and faint extensions of the concentric waves; anterior lunette and a small 
portion of the anterior extremity also nearly smooth ; the ridges where the outer surface is preserved are covered 
with a minute, irregular striation approximately parallel with the margin.- Length from anterior to posterior 
end about five inches two lines, proportional width from beak to opposite ventral margin ;;,, length of anterior 
34 
end #4, depth of both valves (greatest a little behind the beaks) =, length of anterior lunette ;;, width of pos- 
terior lunette =, depth of posterior end about =. 
This fine species is remarkable for the clavate form produced by the gibbosity of the valves near the 
anterior end and the tapering towards the posterior extremity. Of the internal impressions I have only seen the 
anterior adductor, which is broad, rounded, and shallow, with a slight ridge above its anterior margin. The 
only approximation to this species published, that I know, is an indeterminate fragment of one end of a shell 
called S. maxima by Portlock, Geol. Rep. t. 36. f. 1, which is flatter, with smaller beaks, a more truncate 
anterior end, &c. 
Position and Locality—Not uncommon in the earboniferous limestone near Llangollen, N. Wales. 
Explanation of Figures.—PI. 3. F. fig. 12, left valve, natural size, shewing the impression of the anterior 
adductor at the anterior end; fig. 12 a, back view, to shew the wide anterior and posterior lunettes, or inflected 
margins for the external cartilage. 
Sanaurnouites [rtpinompEs (M°Coy). Pl. 3. F. fig. 11. 
Ref—M ‘Coy, Synop. Carb. Foss. Irel. t. 12. f. 1. 
Dese.—Shell much flattened, very elongate, oblong; anterior side short, compressed, semielliptically rounded, 
no byssal furrow defining it from the body of the shell; ventral margin slightly convex; posterior end 
slightly narrowed, obliquely truncate, the slightly oblique angles rounded; anterior side and body of the shell 
