480 BRITISH PALAZOZOIC FOSSILS. | LAMELLIBRANCHIATA, 
that species separates the posterior ear from the body of the shell; the posterior or dorsal slope is also 
straighter, and the posterior wing shorter than in that species. 
I place this fossil in Pterinea rather than Avicula, from the large, strongly marked, anterior adductor 
impression, although it has no hinge-teeth. 
Position and Locality—Carboniferous limestone of Derbyshire; two small specimens (about one and half 
inches long) from Lowick, Northumberland, seem to be the young of this species, although they have the 
posterior wing rather longer than in the normal ones. The original locality was lower carboniferous limestone 
of Millicent, Clane, Kildare (not uncommon). 
PTERINEA LUNULATA (Phill. Sp.) 
Ref. and Syn. = Gervillia id. Phill. Geol. York, Vol. Il. t. 6. f. 12. 
Desc.—Obliquely elongate, narrow, gently arched upwards; posterior slope slightly arched upwards, 
sharply defined, smooth, nearly vertical to the body of the shell and to the posterior wing, becoming gradually 
obsolete at the posterior end; beaks moderately tumid, small, separated by a wide triangular cartilage facet in 
the left valve, marked with coarse sulci angulated towards the beak: anterior end small, obtusely pointed, 
defined from the body of the shell by a narrow oblique sulcus, extending from the beak to the byssal sinus, 
which is rather less than one-fourth the length from the anterior end; the ventral margin moderately convex 
from thence to the posterior end, which is semielliptically pointed: hinge-line about half the length of the 
posterior slope, the flattened posterior wing having its posterior margin so concave near the angle as to render 
it pointed, but the margin slopes obliquely from thence to the posterior extremity of the shell; surface marked 
with coarse, irregular, slightly imbricating lines of growth parallel with the margin. Length from beak to 
13 
posterior end one inch six lines, proportional length of anterior end 55, greatest width from middle of posterior 
43 
slope (at right angles thereto) to the ventral margin %, width of posterior wing =, length thereof along the 
44 25 
hinge-line about =, depth of left valve 5, of right valve ;;;. 
The anterior adductor impression is strongly marked, and on this account I provisionally place this 
shell in the genus Pterinea, although I have not been able to see any traces of hinge-teeth ; the most nearly 
allied shell is the Gervillia (Pterinea) laminosa of Phillips, which has the same large cartilage facet to the 
left valve, but is specifically distinguished by the shorter and more obtuse outline, and most remarkably by the 
posterior wing being only gradually defined from the body of the shell, instead of the sharply defined, vertical 
posterior slope of the present species. 
Position and Locality.—Carboniferous limestone of Derbyshire. 
Genus. PTERONITES. See page 391. 
PTERONITES PERSULCATUS (M/*Coy). PI. 8. F. fig. 1. 
Ref. = M°Coy, Ann. Nat. Hist. 2nd Series, Vol. VII. 
Desc.—Transversely trigonal, right valve gently convex, left valve diagonally tumid, posterior end broad, 
rounded ; posterior wing flattened, large, pointed, reaching nearly as far as the posterior end of the shell ; 
posterior margin concave, and forming a gentle sigmoid curve with the posterior end of the shell; anterior end 
and beak forming a small, convex, obtusely pointed extremity ; a small space of the anterior extremity smooth, 
all the rest of the shell covered with small, coarse, rugged, flexuous, irregular, slightly interrupted ridges, for 
the most part alternately larger and smaller, and less than their thickness apart; those of the posterior wing 
nearly straight, radiating, those of the body arching downwards towards the ventral margin; three or four 
broad, obscure, concentric waves of growth, strongest on the ventral half of the body of the shell, interrupting 
the ridging. Length from beak to posterior margin one inch four lines, proportional length of hinge-line from 
beak to posterior end of wing about #4, width of posterior wing , from middle of hinge-line (at right angles 
thereto) to ventral margin *%, depth of left valve 
16 
100 * 
