450 BRITISH PALALOZOIC FOSSILS. [Bracutopopa,. 
Genus. LEPT/ENA. See page 232. 
Subgenus. STROPHOMENA. See page 241. 
Lepraxa (Strophomena) CRENISTRIA (Phill. Sp.) 
Ref. and Syn. = Spirifera crenistria Phill. Geol. York. Vol. II. t. 9. f. 6, and Port. Geol. Rep. t. 37. f. 5. 
= 0. Sharpei Mor. Cat. 
Desc.—Truncato-orbicular ; hinge-line slightly exceeding the width of the shell, in short slightly acute ears ; 
flat when young; when old the receiving valve is convex at the slightly prominent beak, flat in the middle and 
gently concave or deflected at the margin. Entering valve flattened, slightly concave at the beak, and all 
the rest slightly convex. Cardinal area linear or obsolete in the entering valve, large, triangular in the receiving 
valve, inclining backwards at about 115°, and with a large triangular mesial foramen, the sides of which meet at 
right angles, nearly closed by a convex pseudo-deltidium. Radiating striae strong, (from six to eleven in two 
lines at eight lines from the beak of the ridges, more constantly six in the same space at the margin in same 
specimens at two inches from the beak) thread-like, unequal in thickness, increasing in number towards the mar- 
gin by intercalation of one or three finer ridges, rapidly acquiring the size of the others; spaces between the ra- 
diating striz flat, considerably wider than the ridges, but varying greatly in this respect, closely marked with 
small, deep, irregularly transverse wrinkles (distinct from the much finer transverse regular lines of growth) 
and under the lens, in some states of preservation, sharply striated longitudinally (five or seven strize between 
each pair of ridges). One obscure mesial and two obtuse dental lamelle in the receiving valve, diverging at 
about 95°, forming the posterior boundaries of a broad, ovate, faintly defined, muscular space, irregularly sul- 
cated, about as wide as long, and about half the length of the shell (at two inches long). Width three inches, 
proportional length 7, depth ;°,, height of cardinal area about ;;. 
The striation is very variable, according to the state of preservation; in some the principal striz, being 
nearly a line apart, and the intervening flat spaces having very distinct longitudinal fine lines, internally punc- 
tured, the middle one largest, and crossed by fine, close, deep, irregularly transverse wrinkles; in others the 
intervening strize nearly equal the principal ones in size, and the shell appears more closely and coarsely striated 
subalternately, but both extremes may be seen on the one specimen, and the differences are clearly the result of 
the loss of one or more layers of shell. In some rare cases the transverse wrinkles are the same size and 
distance apart as the longitudinal ridges. I have no doubt the O. Sharpei of Morris is synonymous. The 
great size, more slender ridges, small, irregular, transverse wrinkles independent of the lines of growth, great 
depression or flatness of both valves, and less inclined cardinal area, separate this certainly from the Devonian 
S. umbraculum (Schlot. Sp.) 
Position and Locality—Common in the lower carboniferous limestone of Kendal; common in the black 
upper carboniferous limestone of Derbyshire; in the black impure lowest beds of the carboniferous limestone 
of Ronalds-way, Isle of Man, 
LerT&NA (Strophomena) cyuinprica (J°Coy). 
Ref. and Syn. = Orthis id. MeCoy, Syn. Carb. Foss. Irel. t. 22. f. 1. 
Desc.—Subeylindrical when adult ; hinge-line considerably less than the width of the shell, forming incon- 
spicuous, obtuse-angled, broadly rounded ears. Entering valve evenly gibbous, almost hemispherically arched 
for rather less than an inch from the beak, beyond which the front is gradually deflected into a vertical semi- 
cylindrical front, with subparallel sides; front more convex than the sides; cardinal area obsolete. Receiving 
valve with a wide, triangular, cardinal area, inclining backwards at about 125°; pseudo-deltidium very convex, 
one-third higher than wide, moderately convex in all the rostral portion, becoming gradually concave where it 
approximates the descending front of the entering valve, the profile forming a strong sigmoidal curve, leaving a 
large space between the valves for the animal. Radiating strix filiform, alternately larger and smaller on the 
