426 BRITISH PALAZOZOIC FOSSILS. [Bracuiopopa. 
Subgenus. CYRTIA. See page 191. 
SPIRIFERA (Cyrtia) cusprpata (Martin Sp.) 
Ref. and Syn. = Anomites cuspidatus Mart. Pet. Derb. t. 46. f. 3, 4. = Spirifer id. de Kon. Anim. Foss. Bel. 
t. 14. f. 1. 
Desce.—Pyramidal ; entering valve nearly semicircular, depressed, gently convex ; mesial ridge very wide, 
obtusely rounded, smooth, strongly defined from the beak to the front margin, the sides of which it does not 
equal in length, owing to the sinus being abruptly raised at considerably more than a right angle from the plane 
of the horizontal lateral margins; from fifteen to twenty simple, slightly convex, radiating ridges on each 
side, gradually decreasing to the cardinal angles, becoming obscure by age; beak prominent; mesial septum 
about one-third of the length in old specimens, rather more in small ones. Receiving valve pyramidal ; car- 
dinal area very large, triangular, forming an acute angle at the beak of receiving valve in old specimens, 
lower and more curved in young, varying greatly in height, usually flattened, but varying to slightly concave, 
the beak being either vertical, slightly incurved, or very slightly recurved; triangular opening very large, 
often displaying the internal deep-seated pseudo-deltidium (without perforation, leaving the only opening to the 
shell at its base); mesial hollow very wide, produced into a tongue-shaped lobe in front, sides flattened, lateral 
ribs as in entering valve ; dental lamellze diverging at the same angle as the sides of the mesial hollow ; surface 
smooth, or marked with irregular lines of growth. Width of very large specimen three inches three lines, pro- 
portional length of entering valve in middle %, at sides of mesial fold =, width of mesial sinus %, height of 
80 24 64 
ditto =, length of receiving valve %, apical angle 85°, width of foramen at base 4, height of area §*. Interme- 
57 
diate specimen, width two inches, length of entering valve %, of receiving valve *, apical angle about 85°, 
height of area =, width of opening at base %. Depressed specimen one inch seven lines wide, length of 
35 50 
receiving valve ;%, cardinal angle about 95° to 110°, height of area 3% to *. 
The varieties found at Kendal with a comparatively low cardinal area, as well as that from Tournay figured 
by M. de Koninck as this species, are considered distinct by Mr Sharp, and referred by him to the American 
Devonian 8, macronotus of Hall, characterized by a very narrow foramen, low wide cardinal area, thirty ribs on 
each side, and very strong concentric strie. But from the great number of specimens I have examined, I have 
satisfied myself that the extremes of cardinal area, which I have noted above, pass in the most gradual manner 
from one to the other, and being unaccompanied by change in any of the other characters, cannot possibly be 
admitted as distinct species. The thirty lateral ribs on each side, narrow foramen, and strong transverse 
sculpturing characteristic of the American fossil, are not to be found, I think, in our English carboniferous 
species. The observations of M. de Koninck (op. cit.) exactly accord with my own as to the gradual variation 
of the cardinal area. 
Position and Locality—Not uncommon in the lower carboniferous limestone of Derbyshire ; very common 
in the impure sandy lower beds of carboniferous limestone of Kendal. 
SPIRIFERA (Cyrtia) LAMINOSA (M°Coy). 
Ref.—Id. id. M°Coy, Carb. Foss. Irel. t. 21. f. 4. 
Dese.—-Subrhomboidal or pyramidal; entering valve semicircular, moderately convex ; cardinal angles very 
slightly acute ; mesial fold large, very prominent, rounded, produced into a long rounded lobe, the profile of 
which is very little arched, abruptly defined at the sides from the lateral front margins; five or six large angular 
ribs on each side. Receiving valve subrhomboidal, sides slightly convex ; beak scarcely incurved, much elevated 
by the high, triangular, cardinal area; about six large, equal, angular ribs on each side; mesial hollow wide, 
deep, strongly defined, produced in front when old into a long, tongue-shaped, flattened lobe; profile very 
slightly arched from the beak; surface of both valves strongly sculptured, with subregular, erect, scale-like, 
concentric laminze parallel to the margins, and undulated by passing over the large ribs. Width of old specimen 
one inch six lines; proportional length of receiving valve from beak to lateral margin at mid-lobe ;, projection 
