Bracutopopa.| UPPER PALAZOZOIC MOLLUSCA. 471 
tened at the ears, moderately concave at the sides, and often slightly convex along the middle, marked with 
quincuncially arranged, elongate, oval tubercle-pits, and concentric wrinkles, smaller, closer, and more regular than 
those of the receiving valve. Width of small specimens one inch, proportional length =, depth =, length 
of entering valve 4, depth of entering valve ;;;. At one inch from the beak about four longitudinal rows of 
tubercles in the space of two lines. 
The original Anomites scabriculus of Martin was strongly sulcated longitudinally, the elevated lines swelling 
into alternating elongate tubercles, and thus coincided with the P. guincuncialis of Phillips, which species 
should therefore be suppressed. In my volume on the Carboniferous Fossils of Ireland, I let the P. scabricula 
and P. quincuncialis as understood by Phillips stand, but under both heads I distinctly stated that one of his 
distinctions, namely, the presence in one, and the absence in the other, of a mesial furrow would not hold; it 
is unfortunate, therefore, that in M. de Koninck’s monograph of the genus I should be made to rely on this 
character for distinguishing the species. The connexion of the elongate spine-bases by strong longitudinal 
sulci easily distinguishes this species from the shell named P. pywidiformis by M. de Koninck (which is 
probably Phillips’ P. scabricula) and from all the varieties of P. pustulosa. 
Position and Locality —Not uncommon in the dark carboniferous limestone of Lowick, Northumberland. 
PRODUCTA SEMIRETICULATA (Mart. Sp.) 
Ref. and Syn.= Conch. Anomites semireticulatus Martin, Pet. Derb. t. 32. f. 1. and 2. t. 33.f. 4.=P. antiquatus 
Sow. Min. Con. t. 317. f. 5, 6.= Producta antiquata Koninck, Monog. Prod. t. 9. f. 1. 
Dese.—Rotundato-quadrate when young; extended front becoming prismatic when old; the profile semi- 
circularly arched from the beak to the middle of the descending front; the sides subparallel, rather flattened and 
nearly yertical; the front only slightly concave ; the whole shell and margin nearly regular ; hinge-line equal to the 
width of the shell, forming rectangular flattened ears. Receiving valve very gibbous; with a broad, shallow, mesial 
hollow on the middle of the visceral portion, becoming obsolete towards the beak and on the descending front ; 
visceral portion marked by very numerous (upwards of forty) narrow, slightly undulating, concentric wrinkles, 
which raise tubercles on the longitudinal striz at their intersections, becoming much coarser and spinose on the 
sides; longitudinal strize direct, coarse, rugged, rounded, subequal, separated by sulci of nearly their own width (ave- 
raging four to six in three lines at two inches from the beak), without flexures, simply dichotomising occasionally ; 
no spines on the body of the shell, or only a few small ones, not exceeding the striz in width, and producing no 
irregularities in the striation; a group of six or seven very long thick spines on a nearly smooth space near the 
side margin beneath each ear. Entering valve with the visceral portion nearly at right angles to the front ; beak 
and sides moderately concave, with a distinct, wide, undefined, mesial furrow, becoming obsolete on the de- 
scending front, and reaching only within half an inch of the beak; concentric wrinkles as strong and nearly as 
close as the longitudinal striee, producing a tubercular or pitted, irregular reticulation; the wrinkles become 
larger and fewer on the ears, joining the hinge-line at an obtuse angle. Interior of entering valve with a very 
large, prominent, rostral tooth, from which a mesial septum extends nearly to the commencement of the deflected 
front ; interior of receiving valve, with the striated anterior portion of the muscular impressions nearly twice as 
wide as long, and about a third less than their length apart; dendritic impressions small, and unusually far 
from the beak, lying just between the striated anterior portion of the muscular impressions. Average width of 
adult specimens two inches eight lines, proportional length of visceral portion % in the receiving valve, > in the 
entering valve, depth between the visceral portion of the two valves 4, length of adult unreticulated front ;7,. 
Martin’s figures represent the young shells, which are obscurely trigonal (excluding the ears), and entirely 
reticulated. This is by no means so common a shell as the varieties of the P. Flemingi with which it is 
frequently confounded, but from which it is distinguished by its broader and more cubic form, instead of the 
long, narrow, parallel-sided form of the P. Flemingi var. sulcata ; it has no spines except a patch on the sides, 
(not disposed on a ridge as in that species), has not the small conical ears with large ridge at base, as usually 
seen in that shell, has no mesial furrow near the margin of the deflected front ; and finally, the visceral disk 
is less gibbous and arched, and much more strongly and numerously crossed by concentric wrinkles. 
[rase. tt. ] 3P 
