Bracutopvopa. | LOWER PAL/AKOZOIC MOLLUSCA. 195 
so as to meet in the rostral part, enclosing the large triangular foramen, and again diverging in their 
anterior part, reaching to within one fourth the length of the anterior margin; each side with about six 
thick radiating ridges (ovarian!), and two or four on the middle lobe, all obscurely forking at the margin ; 
casts of entering valve shew two thick diverging dental pits at the beak, a wide shallow mesial depression, with 
an obscure crucial arrangement of four angular ridges defining the muscular impressions; there are three 
or four short, thick, radiating ridges on the small elevated part of the front, and a few very short marginal 
: : ie ee ae : = 
lateral ones; surface smooth. Width of receiving valve nine lines, proportional length varying from ;*, to 
depth of receiving valve ;.. . 
This fossil seems to belong to the same section of Spirifer as the S. Mosquensis of Fischer, as figured by 
de Verneuil in the Geology of Russia, and in which the dental lamellze present the same unusual size and 
curvatures. The less apical angle, shorter mesial fold, and near equality of length and width, as well as the 
generic difference in the internal plates, separate this from the Atrypa (Pentamerus) undata of Sowerby. 
In placing this species in the genus Spirifer, I have been obliged to use a new specific name, as it is 
not, of course, the carboniferous Spirifer crassus of de Koninck. 
Position and Locality —Upper Bala schists and limestones of Mathyrafal, S. of Meifod, Montgomeryshire ; 
very common in the Upper Bala schists of Cefn Rhyddan, Llandovery, S. Wales; Coniston or Bala limestone of 
Coniston, Laneashire; ? schists, Cyrn y Brain, W. of Wrexham, Denbighshire ; fine green conglomerate (Cara- 
doc sandstone) of Moel Seisiog, Llanrwst, Denbighshire; sandy Upper Bala schists of Mathyrafal, Meifod, 
Montgomeryshire. 
100 
1009 
SPIRIFERA RADIATA (Sov,) 
Ref-—Min. Con. t. 493. f. 1, 2. and Sil. Syst. t. 12. f. 6. 
Sp Ch.—Transversely subrhomboidal. gibbous; hinge-line slightly less than the width of the shell; cardinal 
area moderately wide, triangular, curved; cardinal angles obtusely rounded; receiving valve with a large 
incurved beak, and a wide, deep, rounded mesial hollow, extending from the apex to the front margin, which 
is abruptly raised into a deep quadrate sinus; sides gibbous; entering valve with a very prominent rotundato- 
quadrate mesial ridge, strongly defined from the beak to the sinus in the front margin; sides tumid; surface 
radiated with very fine, close, nearly equal, thread-like striz, bifurcating occasionally (23 in 3 lines at 6 lines from 
the beak) ; casts of receiving valve shew the slightly diverging slits of two extremely thick dental lamelle. 
Average width 1 inch 6 lines, proportional length %, length of entering valve *, depth “. 
Position and Locality —Common in the Ludlow rock, Keeper’s Lodge, Goldengrove, Llandeilo, Caermar- 
thenshire. 
SPIRIFERA SUB-SPURIA (d’O7b.) 
Ref. and Syn.—@Orb. Prod. Pal. p. 42. = Spirifer octoplicatus Sow. Sil. Syst. t. 12. f. 7. (not of Min. 
Con.) = S. plicatus Sharp. Quart. Geol. Journ. Vol. IV. (not of Hon.). 
Sp. Ch.—Rhomboidal, hinge-line nearly as long as the shell is wide, cardinal angles obtusely rounded ; 
cardinal area rather broad, slightly curved, triangular; entering valve convex, with a strongly-defined mesial 
ridge, divided except near the beak by a deep rounded sulcus, each half being about the size of the adjacent 
lateral ridges, the separating sulcus at margin being about as wide as the ribs, each side with four or five 
strongly defined rounded ridges; receiving valve very tumid, much arched towards the incuryed beak, mesial 
sulcus as large as the opposite ridge, very deep, rounded, without ribs, bounded by a very strong rounded ridge 
on each side, much more prominent than the three or four lateral ribs; surface slightly marked with delicate 
concentric lines of growth ; average width five lines, proportional length ®., length of entering valve *., depth 
about @- 
The casts shew the two dental lamellz in the receiving valve very thick but short, and a faint trace of the 
mesial septum on the ridge of the entering valve. I do not think, with Mr Davidson or M. d@Orbigny, that 
cc2 
