Bracutoropa. | LOWER PALAXOZOIC MOLLUSCA. 243 
Bala, Merionethshire (a coarse variety); Caradoc sandstone, top of Moel Seisiog. Doubtful specimens in 
the Bala schists of Pwllheli, Caernarvonshire. 
Leprzna (Strophomena) EuGLYPHA (Dal. Sp.) 
fef.—Sow. Sil. Syst. t. 12. f. 5. Davidson, Bull. de Ja Soe. Géol. de France, 2nd Series, Vol. V. t. 8. f. 4. 
Sp. Ch.—Young shells, and rostral portion of adults for nine or ten lines from the beak, flattened ; very 
slightly concave in the entering valve, and very slightly convex near the beak of the receiving valve ; hinge-line 
exceeding the width of the shell; front obtusely narrowed ; in the adult state the margins of both valves bent 
together with a rapid curve towards the receiving valve into a long semicylindrical front, nearly at right angles 
to the rostral portion, with broad, slightly-flattened sides, and an obtusely-rounded, narrowed front: surface 
covered with slightly-rugged, irregular, filiform ridges, seven in three lines, at the curved front, between the 
rostral and descending portions, and haying there irregularly from one to four longitudinal striz between each 
pair; on the deflected front of old individuals the intervening striae gradually acquire the size of the primitive 
ones, but little more than their thickness apart (ten or eleven in the space of three lines), with or without a single 
intervening line: cardinal area rhomboidal, narrow ; a wide, triangular opening in the middle of the receiving 
valve nearly closed by the pseudo-deltidium ; area at the entering valve narrow, with a trifid rostral tooth in the 
middle ; interior of receiving (concave) valve without developed cardinal teeth, with a large pair of oblong, 
faintly-radiated, adductor impressions, the prominent boundaries of which form a waving incurved ridge on each 
side, occupying more than two-thirds of the length of the rostral part of the shell; between them is a small 
mesial septum, which in the cavity of the beak becomes much thickened, apparently to support the pseudo-del- 
tidium ; interior of entering convex valve with two bifid, diverging, cardinal teeth, and an obscure mesial 
septum, having on each side near the beak a circular pair of small adductors, immediately in front of which 
a pair of anterior adductors; substance of the shell with very large punctures. Width two inches two 
45 55 
lines, proportional length of flattened rostral portion “, of deflected front in old individuals %, height of 
cardinal area }°. 
The Leptena imbrex of authors so closely allied to this species in general appearance, has the receiving 
instead of the entering valve the convex one, as may be well seen from the figure given by Mr Davidson, in 
Bull. de la Soc. Géol. de France, 2nd Series, Vol. V. t. 3. f. 8, although the character has not, I believe, 
been noticed before. 
Position and Locality—W oolhope limestone of Littlehope; very common in the Wenlock limestone of 
Dudley, Staffordshire ; Aymestry limestone of Leintwardine, Shropshire ; limestone of Clungunford, Shropshire ; 
common in the Wenlock limestone of Woolhope. 
LertaNaA (Strophomena) ?¥FiLosa (Sow. Sp.) 
Ref. and Syn.= Orthis filosa Sil. Syst. t. 13. f. 12. Davidson, Bull. Géol. S. de France, 2nd Series, 
Vola Vetaer ts) 
Sp. Ch.—Transversely semielliptical, both valves nearly flat, very slightly convex, greatest width along the 
hinge-line ; cardinal angles acute; cardinal area very narrow: surface of both valves radiated with fine sharp 
prominent ridges, having between them from three to five very much finer strie, the odd middle one of which 
becomes gradually larger towards the margin; intervening sulci very narrow, minutely punctured, about thirty 
to forty in the space of two lines at four lines from the beak: interior of receiving valve with two very long 
slightly incurved dental lamelle, diverging at only 55° to 65°, reaching about half the length of the shell, 
enclosing between them the very narrow bilobed muscular impressions, which are defined anteriorly by a deep 
V-shaped boundary, from the apex of which a sharp mesial ridge is continued to the beak: internal cast of 
entering valve with two small deep pits of the bifid rostral tooth, and two short slightly recurved slender 
cardinal teeth, diverging close to the hinge-line; two very short, deep, ovate, muscular impressions situated 
112 
