LAMELLIBRANCHIATA. | LOWER PALAZOZOIC MOLLUSGCA. 
bo 
~j 
I 
SANGUINOLITES DECIPIENS (M°Coy). PI. 1. I. fig. 24. 
Sp. Ch—Elongate, oblong, dorsal and ventral margins subparallel; beaks incurved, small, depressed, 
about one-fifth the length from the anterior end; hinge-line long, not elevated, (the inflected edges forming 
a nearly horizontal posterior lunette extending its entire length); cardinal angle about 115°; anterior end 
rounded, narrowed by a large elongate, elliptic lunette; a strong sigmoidally contorted diagonal ridge extends 
from the beak to the respiratory angle; posterior slope steeply inclined ; posterior end slightly oblique, sub- 
truncate, rounded; ventral margin with a wide, rather deep sinus in the middle, from which a wide concavity 
extends nearly to the beak, and from the diagonal ridge to the anterior end, which is convex anterior to 
the beaks; surface marked with sharp concentric wrinkles from the anterior lunette to the diagonal ridge. 
Length eight lines, in proportion to the length greatest width (from beak to opposite margin) 4, length of 
anterior end ;;;, from beak to end of hinge-line =, greatest depth of one valve (about middle of diagonal 
ridge) =. 
I have seen numerous specimens of this species from the Upper Ludlow rocks usually confounded with 
the so-called Cypricardia cymbiformis (Sow.), which it strongly resembles at first sight, although the anterior 
end is considerably longer. That fossil, however, has simple erect dorsal margins, and belongs to the genus 
Orthonotus, as restricted in this work, while the distinctly inflected dorsal edges forming the elongate, concave, 
posterior lunette shew the present species to belong to the genus Sanguwinolites. 
Position and Locality—Not uncommon in the Upper Ludlow rock of Benson Knot, Kendal, Westmore- 
land, and in the micaceous grits of Llechclawdd, Myddfai, near Llandovery, S. Wales; greenish schists of 
Balmae Shore, Kirkcudbright. 
Explanation of Pigure—P\. 1. 1. fig. 24. Natural size, right valve. 
SANGUINOLITES INORNATUS (Phill. Sp.) 
Ref. and Syn. = Orthonota inornata Phil., Mem. Geol. Surv. Vol. II. t. 19. f. 3. 
Sp. Ch.—Elongate, oblong, slightly contorted sigmoidally; length about three times the width; beak 
narrow, about one-fifth of the length from the anterior end, which is slightly narrowed, subquadrate; pos- 
terior end not expanded, the margin slightly oblique, truncate: a strong rounded diagonal ridge extends 
from the beaks towards the respiratory angle with a gentle sigmoidal curve; behind this ridge the posterior 
slope is regularly flattened, and in front of it the sides are widely concave up to the gently convex anterior end ; 
ventral margin slightly concave, dorsal margin slightly curved upwards; inflected portion concave, narrow ; 
internal cardinal ridge strong ; surface marked with concentric small plicze of growth. Width six lines, depth 
of one valve two and half lines, (specimen too imperfect to give the length). 
This species reminds us of the large S. contortus (M*Coy) of the Irish carboniferous limestone, by the 
sigmoidal twist of its diagonal ridge, &c.; it is very distinct from all the other Lower Palzeozoic forms. 
Position and Locality.— Limestone of Balmae Shore, near Kirkcudbright. 
Genus. LEPTODOMUS (A/°Coy). 
Gen. Char.—Shell excessively thin, short, oblong, tumid; subequivalve, very inequilateral ; beaks large, 
tumid, incurved; anterior side very short, obtusely rounded, slightly gaping; a deep, sharply-defined, ovate 
lunette beneath the beaks; posterior end broad, rounded, gaping; dorsal and ventral margins with a slight 
upward curvature, posterior slope compressed, sides sulcated, parallel with the ventral margin ; often a shallow 
depression from the anterior third of the ventral margin towards the beaks; dorsal margin inflected nearly 
at right angles to form a nearly parallel-sided concave posterior lunette as long as the hinge-line ; no hinge- 
teeth; a narrow sulcus in each valve runs from the beak towards the posterior end, nearly through the middle 
of the posterior slope, leaving a similar sulcus in the cast ; (no cardinal ridge) ; impression of the two adductor 
muscles and similar pallial scar very faint. 
