276 BRITISH PAL/EOZOIC FOSSILS. [ LAMELLIBRANCHIATA. 
cartilage short, external ; cardinal margin inflected to form a defined, concave, dorsal lunette the whole length of 
the shell; beneath the hinge-line, a long, posterior, lateral tooth or ridge in each valve, the place of which is 
sometimes marked by a slight depression outside; cardinal teeth usually obsolete ; two strong muscular impres- 
sions at the anterior end and one faint posterior one ; pallial scar entire. 
The group of shells I unite under this name are only known in the fossil state ; they are intermediate in 
many of their characters between the Mytilidw and the Astartidw, having the form, and usually the edentulous 
hinge and byssal furrow of the former, with the double, anterior, muscular impressions and hollowed back pro- 
duced by the anterior and posterior lunettes, and the exterior cartilage of the latter. 
Genera :—Ist, Sanguinolites ; 2nd, Grammysia ; 3rd, Leptodomus ; 4th, Myoconcha. 
Genus. SANGUINOLITES (Af/Coy). 
Syn. < Cypricardites (Conrad) < Allorisma (King). 
Gen. Char.—Subequivalve, oblong, very much elongated, dorsal and ventral margins subparallel, straight 
or a little arched upwards; sides compressed or diagonally gibbous, from the beak to the posterior ventral 
angle; beaks small, close to the anterior end, which is very short and rounded ; posterior end subtruncate ; 
byssiferous notch and furrow present, or obsolete; hinge nearly as long as the shell, margin inflected to form 
a long posterior lunette ; surface generally marked with wrinkles parallel with the anal and ventral edges ; one 
large oval adductor muscular impression in front of the beak surmounted by the small impression of the 
retractor muscle of the foot, both haying a strong internal ridge behind them; shell thin; posterior adductor 
large, superficial; cartilage external ; an internal thick cardinal ridge close to and nearly parallel with the 
hinge-line in both valves in most species; pallial impression entire. 
In the two anterior muscular impressions and internal and external characters of the hinge-line, &c., this 
genus agrees so closely with M/yoconcha, that 1 have no hesitation in placing them in the same family. The 
pallial impression is entire, but very difficult to see in some of the species, in others (S. regularis) it is clear, in 
some of the Lowick specimens in the Cambridge collection. Since I published this genus (Synop. Carb. Fos. 
Ireland), Prof. King published his genus AJ/orisma, including the present shells (the peculiarity of whose 
inflected dorsal margin he notices), but supposed them to be sinupallial, which certainly is not the case in the 
Paleozoic shells, and embracing at the same time the totally different oolitic fossils called Myacites by 
Schlotheim, Lutraria prisca (Gold.), and the like, which have simple erect dorsal margins, and deeply sinuate 
pallial impressions. 
SANGUINOLITES ANGULIFERUS (M/‘Coy). PI. 1. K. fig. 19 and 20. 
Ref.—ld. M*Coy, Ann. Nat. Hist. 2nd Series, Vol. VII. p. 56. 
Sp. Ch.—Oblong, length three times the width; beaks small, half the width from the anterior end, which 
is subquadrate, rounded ; posterior end subtruncate not oblique, scarcely wider than the width of the shell 
from the beak to the ventral margin; dorsal and ventral margins straight, almost parallel; a strong diagonal 
ridge runs from the beak to the inferior posterior angle, immediately in front of which is the deepest part of 
each valve; from the beak to the anterior end is marked by eight or ten narrow rounded ridges, running 
obliquely downwards and backwards towards the middle of the ventral margin, a few of them about the middle 
of the shell met at an acute angle by a few, more nearly vertical ridges, proceeding from the great diagonal 
ridge; most of both sets of ridges go towards the ventral margin; they are separated by flat spaces wider 
than their own diameter ; the posterior slope is divided into three broad, rounded radiations by three shallow 
impressed lines, crossed by irregular wrinkles, parallel with the posterior margin; all the ridges are slightly 
nodulated by the faint plicee of growth ; posterior dorsal lunette very narrow, concave, horizontal (or perpen- 
dicular to the plane of the valves). Length one inch four lines; proportional width *. 
Position and Locality —A specimen of the right valve shews rather more of the angular ridges, though 
a smaller individual than one of the left side. Rare in the tilestone of Benson Knot, Kendal, Westmoreland. 
Explanation of Figures.—P\. 1. K. fig. 19. Left valve, natural size ; fig. 20, right valve. 
