246 BRITISH PALALOZOIC FOSSILS. [ Bracuiopopa. 
LerT&naA (Strophomena) stmuLAns (M°Coy). Pl. 1. H. fig. 33, 34, 35. 
Ref.—Id. M°Coy, Ann. Nat. Hist. 2nd Series, Vol. VIII. p. 403. 
Sp. Ch.—Truncato-elliptical ; hinge-line slightly exceeding the width of the shell, forming short, rounded, 
semicylindrical ears, from a more or less pronounced indentation of the lateral margins; front wide, elliptically 
rounded; entering valve gently and slightly convex for about nine lines from the beak, and then more rapidly 
arched towards the receiving valve, to a position sometimes nearly at right angles with the rostral portion ; 
receiving valve nearly as concave as the entering valve is convex externally, except near the beak, which is 
convex; cardinal area rather low, triangular, and nearly at right angles to the plane of the lateral margins ; 
foramen broad, triangular, closed by the pseudo-deltidium, except at the apex, where there is a tubular 
perforation (leaving a little columnar stem-like portion of matrix projecting from the apex of the cast); cardinal 
teeth very small, bifid, diverging at 115°; the dental lamellze originating from them converge under the muscular 
impressions, so that their inner, gently-incurved edges touching the shell, diverge at about 65°; muscular 
impressions undulate-orbicular, about a fifth wider than long, reaching rather less than half the length of the 
shell; surface sometimes with a few oblique concentric plicee on the ears, regularly radiated with very fine, 
slightly-irregular striae, about twenty-five to thirty in two lines at six lines from the beak, and at that dis- 
tance usually every fifth, seventh, or ninth of the strize larger than the others, but near the beak they often 
seem simply alternate in size, the intervening delicate sulci closely punctured. Width one inch ten lines, 
proportional length of rostral portion about ;*, more deflected front about 55, depth at middle of length =. 
This species in size, form, striation, and tubular perforation of the apex of the beak, almost exactly resembles 
the Leptena alternata (Conrad), but differs in haying the receiving or foraminated valve concave, instead of being 
the convex one; the striation is also finer and flatter, or more uniform, which with the greater deflexion, or 
arching of the valves, also separate it from the S. grandis. 
The specimens from Blain y Cwm and Goldengrove are netted by a beautiful little species of Vioa branching 
frequently, nearly at right angles, forming straight, forking, or angularly-bending channels, one fourth of 
a millimetre in diameter, the branches being at a little more or less than a line apart, and either in the plane of 
the valves or at right angles to it, leaving round perforations. 
Position and Locality—Not uncommon in the Bala schists of Cefn Coch, Glyn Ceiriog, Denbighshire ; 
in the olive schists of Goldengrove, Llandeilo, Caermarthenshire ; Bala schists of Blain y Cwm, W. of Nantyre, 
Glyn Ceiriog, Denbighshire ; and one doubtful specimen in the sandy schists of the Malverns, Worcestershire. 
Explanation of Figwres.—P1. 1. H. fig. 33, convex, or entering valve, natural size, from the schists of 
Cefn Goch, with a portion of striz magnified; fig. 34, concave or receiving valve, shewing the cast of the 
tubular foramen in the beak ; fig. 34 a, longitudinal section ; fig. 35, internal cast of muscular impression from 
Malvern. 
LepTa@na (Sirophomenad) SPiRIFEROIDES (M/°Coy). 
Ref.—ld. M°Coy, Ann. Nat. Hist. 2nd Series, Vol. VIII. p. 402. 
Sp. Ch.—Subrhomboidal ; sides rather depressed ; only slightly convex ; hinge-line as wide as the shell ; 
cardinal angles square, or slightly acute ; sides subparallel, slightly 
rounded ; front very abruptly raised into a quadrate sinus, one- 
third wider than high, from which a very prominent, rotundato- 
quadrate mesial ridge extends, sharply defined, to the beak; and 
an almost equally deep and strongly defined, flattened, mesial 
hollow extends to the beak of the receiving valve; both valves 
tne ee ing postead tooth act Wie duehat  Yadiated with subequal, thread-like ridges, occasionally dichoto- 
sulcation on part of the shell in lower part. - 5 * . : 
Right-hand Figure —-Cast‘of receiving valve,shewing  Mising (about fourteen in three lines at six lines from the beak) : 
the impressions of the lateral teeth, and the slender. Omid . . . 
Ecanedicastiotaneanicaltoramient’ 7 sre casts of receiving valve shew the closed cicatrized foramen, with 
a long, slender, cylindrical extension of matrix, half a line thick, arching from the apex of the beak into the 
