Bracuropopa. | UPPER PALZOZOIC MOLLUSCA. 427 
of mid-lobe beyond the side margins %, height of cardinal area 3, width of foramen at base “4, width of mesial 
y g g 
sinus at front {3, depth of entering valve =. 
This is a very beautiful species when well preserved, from the elegant scale-like sculpturing of the surface, 
which gave it its name; the small number of the lateral angular ridges separates it from allied species. 
Position and Locality—Not uncommon in the carboniferous limestone of Derbyshire. 
Subgenus. MARTINIA. See page 192. 
SPIRIFERA (Martinia) pEcoRA (Phill.) 
Ref—Phill. Geol. York. Vol. II. t. 10. f. 9. 
Dese.—Suborbicular, very inequivalve and gibbous ; hinge-line equalling about half the width of the shell ; 
cardinal angles and sides semicircularly rounded ; entering valve rounded, evenly gibbous along the middle and 
near the beak, which is unusually large and prominent ; surface arching rather quickly, with moderate convexity, 
to the side margins; lateral margins horizontal, straight ; a rather wide, shallow, defined sinus in the front 
margin, producing no distinct mesial ridge; in most specimens a very narrow mesial sulcus extends nearly to 
the beak; cardinal area distinct; receiving valve extremely gibbous about the middle, greatest depth at about 
one-third the length from the beak, from whence the surface arches rapidly with moderate convexity to the 
front margin, and slopes very rapidly, with slight convexity, to the side margins; beak thick, elevated, very 
slightly incurved, having the appearance of being thrown remarkably back from the beak of the entering valve by 
the height of the cardinal area, which is triangular, slightly concave, sharply defined, and standing at an angle of 
about 95° to 100° with the plane of the lateral margins; foramen very large, triangular, as high as wide; a very 
narrow mesial sulcus extends from the middle of the wide shallow depression in the front margin nearly to the 
beak. When partially decorticated, surface marked from the beak to the margin with straight filiform ridges, 
separated by much wider, flat spaces (five to six in the space of three lines) ; shell-texture very minutely fibrous. 
Width of average specimen one inch six lines, proportional length of entering valve ;j,, length of receiving valve 
A 20 
, width of hinge-line +, height of cardinal area =, depth of entering valve *, depth of receiving valve *, width 
8 0 g P g P g 00 
10 
of sinus in front margin ;\, depth thereof >; of large, unusually wide specimens, width one inch nine lines, 
80 86 
length of entering valve =, of receiving valve about =, width of hinge-line {*, height of cardinal area 4, width 
of sinus in front margin =, depth thereof =, depth of entering valve =>, depth of receiving valve +. 
This is a very distinct species, totally different from S. (17.) glabra, with which most continental authors 
group it, by the singular elevation of the beak, from the height of the cardinal area, at even more than right 
angles with the plane of the lateral margins, instead of the beaks approaching each other. 
Position and Locality —V ery common in the lower black limestone of the Isle of Man; rare in the carbo- 
niferous limestone of Kendal ; rare in the grey lower carboniferous limestone of Derbyshire. 
SPIRIFERA (Martinia) ELLIPTICA (Phill. Sp.) 
Ref. and Syn.=S. elliptica Phill. Geol. York. Vol. II. t. 10. f. 16. (not a good figure) ; = 8. Zineatus Var. de 
Kon. Anim. Foss. Bel. t. 17. f. 8 ¢ (not the other figures). 
Desc.—Transversely elliptical, moderately convex ; hinge-line rather more than half the width of the shell : 
beaks remote, middle of front margin raised into a wide, rounded, or rotundato-quadrate sinus, at an angle of 
about 105° with the plane of the lateral margins; sides narrow, semielliptically rounded; entering valve gently 
and evenly convex, the mesial ridge scarcely perceptible, except at the margin, from the more abrupt curve of 
the sides towards the lateral margins; greatest depth at about one-third from the beak, which is small, slightly 
prominent. Receiving valve moderately and evenly gibbous, with a rounded mesial hollow, extending distinctly 
to the apex of the beak ; beak rather small, only moderately incurved, and rather remote from the beak of the 
entering valve by the height of the cardinal area; surface of both valves marked with concentric, nearly equal, 
regular, slightly prominent ridges (seven in three lines at six lines from the beak), becoming gradually obsolete 
