446 BRITISH PALALOZOIC FOSSILS. [Bracutopopa. 
and at the same time receives from one to nine subangular, usually simple, plaits; sides of the valve flattened 
towards the margins and nearly straight, receiving the same number of ridges as in the entering valve, at a 
distance varying from two to five lines. Width of rather large specimen one inch two lines, proportional length 
of receiving valve ~, of entering valve {;,, width of sinus at base ;%, depth thereof ;{;, depth of entering valve *, 
depth of receiving valve ;;;,, length of rostral chamber ;,, width ,;;, length of mesial septum in entering valve 3%. 
The above measurements give the ordinary proportions of this very common species, but many specimens 
are proportionally longer, and some more depressed. I have traced the passage so perfectly between the C. 
Schlotheimi with one, two, three, four, or five mesial ridges to the large C. multiplicata of King, in which they 
vary from four to nine, that I can have no doubt of the latter species being founded merely on very fully grown 
examples of the former one. In very old specimens, intermediate ridges make their appearance between several 
pairs of the primary ones, and even in small specimens, at four or five lines from the beak a bifurcation is occa- 
sionally seen of one or other of the ridges. 
The greater number of specimens have the greatest width slightly in front of the middle, but in the most 
elongate form it is at two-thirds the length from the beak. Professor King figures some specimens shewing a 
shelly flattened expansion, more than a quarter of an inch wide round the margin (as in Athyris paradoxa, A. 
planosulcata, &c.), and also the very much branched impressions of the pallial vessels, the main trunks of which 
he represents as forming a small, nearly circular, loop on each side, starting from the end of the mesial septum 
and arching successively forwards, outwards, and backwards, nearly to the point of starting, the branches 
towards the margin being given off from the outer side of these loops. 
Position and Locality.—Very abundant in the Permian magnesian limestone of Humbleton. 
CAMEROPHORIA suLcIROsTRIS (Phill. Sp.) 
Ref. and Syn. = Terebratula sulcirostris Phill. Geol. York. Vol. IL. t. 12. f. 31 and 32 + 7. ventilabrum id. 
id. t. 12. f. 36, 38, 39. 
Dese.—Rotundato-trigonal, or subovate ; lateral margins nearly straight, commissures acute; middle of 
front margin very abruptly raised into an oblong or slightly rounded sinus. Entering valve moderately and 
evenly gibbous, the broad mesial ridge only slightly defined or elevated near the margin; profile regularly arched 
from the beak to the front margin, so that the greatest depth is about the middle of its length, mesial ridges 
five to nine, angular, simple, or in old specimens the outer one on each side with a slight bifurcation at the 
margin ; lateral ridges five to seven on each side, about equal to the mesial ones, also simple except at the edge 
of very large individuals ; all the ridges obsolete on the rostral portion, leaving a space round the beak, of three 
or four lines, smooth. Receiving valve with a very large prominent beak, to which the sides converge at an 
angle of 87°; the posterior lateral margins abruptly deflected near the beaks, to form a flattened space, confined 
to this valve, and defined by an obtusely rounded angulation; the smooth rostral portion (about three or four 
lines from the beak) convex, moderately tumid, beyond which the sides are flattened or slightly concave, each 
bearing seven or eight straight angular ridges; mesial sinus abruptly formed after two or three lines from the 
beak, at the same time that the mesial ridges appear, which are usually four in number; middle of the mesial 
hollow flattened; sides steep, smooth. Width of small specimen eight lines, proportional length of receiving 
valve *., length of entering valve 74, depth of entering valve at two-thirds from the beak ;%,, greatest depth of 
receiving valve at one-fourth the length from the beak ;{;, width of mesial sinus ;5;, height thereof 5; greatest 
depth of both valves at right angles to plane of lateral margins ;;;. 
The large smooth rostral space of each valve from the ribs not extending more than from two to three lines 
from the apex, separates this species from H. pleurodon or H. flewistria. The above description is from an 
Irish specimen in the collection; the English ones being considerably larger, but crushed and imperfect. The 
chamber in the beak of the receiving valve is very small, but the mesial septum formed by the junction of its 
walls is strong, and nearly as long as the mesial portion; the mesial septum in the entering valve is only about 
two lines long. 
Position and Locality —Not uncommon in the black limestone overlying the main limestone of Derbyshire, 
