bo 
~I 
bo 
BRITISH PALALOZOIC FOSSILS. [ LAMELLIBRANCHIATA. 
Distinguished from the A. quadratus (M°Coy) by its greater proportional length, rather more oblique 
posterior end, &e. 
Position and Locality.—Rare in the grey micaceous beds at Llechclawdd, Myddfai, near Llandovery, 
S. Wales. 
ANODONTOPSIS QUADRATUS (A/°Coy). Pl. 1. K. fig. 10. 
Ref—Id. M°Coy, Ann. Nat. Hist. 2nd Series, Vol. VII. p. 55. 
Sp. Ch.—Rotundato-quadrate, slightly oblique, width about three-fourths of the length, compressed, slightly 
and evenly convex, the posterior ridge obtuse, and posterior slope obscurely marked ; beaks very small, sub- 
central; anterior and posterior sides of nearly equal width, the former broadly rounded, the latter with an 
obscure, slightly oblique truncation; dorsal margin slightly arched, ventral margin nearly straight, slightly 
convex. Width nine and half lines; length one inch. 
The peculiar figure produced by the shortness of the posterior side, and less convexity, easily distinguish 
this from the A. davis (Sow. sp.) Casts shew the anterior ovate adductor, with a faint clavicular ridge extending 
from in front of the beak to its upper posterior edge; a short cardinal tooth under the beak, and the slender 
anterior and posterior lateral teeth close under the margin, the latter extending almost to the end of the 
hinge-line. 
Position and Locality.—Common in the tilestone of Storm Hill, Llandeilo, Caermarthenshire. 
Explanation of Figure.—P\. 1. K. fig 10. Natural size, right valve. 
ANODONTOPSIS SECURIFORMIS (J/°Coy). Pl. 1. L. fig. 9. 
Ref—ld. M°Coy, Ann. Nat. Hist. 2nd Series, Vol. VII. p. 55. 
Sp. Ch.—Subrhomboidal, compressed, sides evenly convex ; diagonal ridge angular, sharply defined towards 
the beak ; slightly concave towards the posterior slope, which is flattened and steep; beaks small, prominent, 
about one-fourth of the length from the anterior end, which is semicircularly rounded ; ventral margin regularly 
convex ; posterior end narrowed, obliquely truncated, with a straight edge; hinge-line straight, as long as the 
truncated posterior edge; internal posterior cardinal ridge very delicate, close under the hinge-line; anterior 
adductor small, oval, with a short slender ridge from the beak to its posterior edge. Length ten lines, pro- 
portional width 5%, length of anterior end ;;;, length of anal edge ,{,, depth of one valve ;;. 
There is some slight variation in the proportional width of this species ; the shortest varieties of which are 
however much larger and with a more acutely truncated posterior end than the Cypricardia deltoidea or 
Tsocardia axiniformis (Phil.) of the carboniferous and ? Upper Devonian (of S. Petherwin) rocks, to which the 
species is most allied. 
Position and Locality—Common in the green micaceous quartzite (Upper Ludlow) of Benson Knot, 
Kendal, Westmoreland. 
Explanation of Figures.—P1.1.L. fig. 9. Right valve, natural size, elongate variety ; fig. 9a, left valve, 
of short variety. 
Genus. LYRODESMA (Conrad). 
Syn. = Actinodonta (Phill.) 
Gen. Char.—Equivalve, inequilateral, subrhomboidal, anterior side rounded, posterior side obliquely trun- 
cated; two small muscular impressions and an entire pallial scar; about eight straight radiating teeth 
diverging from the beaks. 
LyRoDESMA PLANA? (Conrad). PI. 1. K. fig. 17. 
Ref—Annual Geol. Rep. and Hall, Pal. N. York, t. 82. f. 11. 
Sp. Ch.—Ovato-rhomboidal, compressed; beaks obtuse, prominent, rather nearer the anterior than 
posterior side; anterior side rounded; ventral margin convex, posterior end broad, obliquely truncated ; posterior 
