LAMELLIBRANCHIATA. | UPPER PALZOZOIC MOLLUSCA. 517 
which in old specimens it is gently concave, rising conoidally near the hinge-line, to form the slender, anterior 
rostrum; ventral margin convex, most so near the bounding angulation of the anterior space; posterior end 
compressed, rotundato-trigonal, slightly rounded at the posterior gaping margins, which are separated from the 
ventral margin by a very slight sinus, from whence to a little behind the beaks is a very faint concavity or 
posterior slope, where the compressed posterior end joins the body of the shell, which is very gibbous, most so 
about the middle. Surface when well preserved nearly smooth, or with fine concentric strize of growth; when 
partially decorticated, shewing strong, regular, radiating ridges, extending from the beak to the margin (six in 
two lines at four lines from the beak), abruptly smaller on the anterior depressed space (twelve in two lines). 
Average length of posterior end from beaks seven lines, proportional length of anterior rostrum about “4, its 
width at base about ;{;, depth from beak to opposite point of ventral margin 3, from beak to extremity of 
cordate space +, width of cordate space 4, depth of both valves =. 
On looking carefully to Mr Sowerby’s original figures, I think with M. de Koninck (and as Professor 
Phillips partially thought) that the true Cardium aliforme is the mountain-limestone species called Pleuro- 
rhynchus minaxz by Phillips; but I think, with Professor Phillips, that Goldfuss and most authors have confounded 
two species under the name C. aliforme. The true C. aliforme of Sowerby is a distinctly carboniferous type, and 
his figure agrees with P. minaz; the Eifel, and generally Devonian, form to which Professor Phillips in his 
Paleeozoic Fossils proposed to transfer the name C. aliforme, might perhaps retain the name given it by 
Schlotheim (C. hystericus). The strongly defined, depressed, anterior space, with its abruptly finer and more 
numerous ridges than occur on the rest of the shell, mark the species very distinctly, the boundary of the 
cordate space not forming the deepest part of the shell, the anterior profile of which is therefore obtusely 
rounded close to the bounding angulation. In some internal casts from Lowick I have seen a trace of the 
single cardinal tooth, and an anterior and posterior lateral tooth, as well as the entire pallial scar; but I 
cannot be sure of the position or number of the muscular impressions. M. d’Orbigny, in his Prodrome, makes 
the Cardium Ouralicum a synonym of this species, I suppose by mistake, as it agrees rather with C. rostratum, 
and has none of the characters of the present species. 
Position and Locality—Common in the carboniferous limestone of Derbyshire; in the carboniferous lime- 
stone of Malham Moor, Yorkshire; in the impure carboniferous limestone of Lowick, Northumberland. 
CoNOCARDIUM ROSTRATUM (Mart. Sp.) 
Ref. and Syn.= Conch. Arcites rostratus Martin, Pet. Derb. t. 44. f. 6.=Cardium elongatum Sow. Min. Con. 
t. 82. f. 3. = Pleurorhynchus elongatus (Sow.) Phill. Geol. York. Vol. II. t. 5. f. 28. = Cardiwm Ouralicum 
M. V. K. Geol. Russ. t. 20. f. 11. 
Desc.—Subfusiform or subclavate; anterior end obtusely conical, extending into a short, thick, triangular 
rostrum, from the base of which the surface slopes gradually to the deepest part of the shell, which is opposite 
the beak, at right angles to the hinge-line, and forms an obtusely rounded prominence, from whence the body 
of the shell slopes rapidly, with little convexity, towards the posterior end, from which it is separated by an 
oblique shallow sulcus, extending from a little behind the beaks to the posterior third of the ventral margin, 
which it sinuates ; beyond which sinus the narrow, posterior, gaping extremity is strongly rounded at the margin, 
and slightly convex on the sides; beaks narrow, tumid, prominent, at about the anterior third of the shell; 
shell when well preserved thick and nearly smooth, only marked with fine concentric lines of growth; when 
decorticated the whole surface is covered with rather coarse sulci and ridges, radiating from the beak, being 
nearly equal, but those of the posterior extremity rather narrower, more rugged, and alternate in size. Length 
from beaks to posterior extremity nine lines, proportional length of anterior rostrum from beak about “4 (slightly 
broken), depth from beak to opposite ventral margin 4, greatest depth of both valves 2, depth of both valves 
half way between the beak and posterior end *. 
If it were not for the shortness of the anterior rostrum in the figure t. 20. f. 11. of the Geology of Russia, 
I should have no doubt that the Cardiwm Ouralicum of MM. Murchison, de Verneuil, and Keyserling, 
was identical with this species, because I have constantly found the oblique suleus between the body and 
