Bracuropopa.] LOWER PALAZOZOIC MOLLUSCA. 235 
I mentioned of longitudinal striz; the better specimens now before me are all distinctly striated, but so 
much alike in other respects that I have no doubt of their identity, the geological position of each being 
alike. The specimens of this variety which shew the dental lamelle seem to have them more divergent, 
and the muscular impressions wider than the typical form. Some specimens of this variety have upwards 
of twenty concentric rows of faint, interrupted, concentrig undulations, giving a curious rippled appearance 
to the surface, from which I named the species, when I believed it distinct. 
Position and Locality—Var. 8. wndata. Common in the Bala limestone of Llandeilo, Caermarthen- 
shire ; Bala limestone of Llwyn-y-ci, N.W. of Bala; Bala limestone of Pont y Glyn Diffwys, W. of Corwen, 
Merionethshire ; Bala limestone of Brynbedwog Quarry, near Bala; ditto Cymmerig, E. of Bala; Bala 
schists of Bryn Melyn, and Gelli Grin, Bala, Merionethshire; Bala schists of Oyrn-y-brain, W. of Wrexham, 
Denbighshire; Bala sandstone of Alt yr Anker, Meifod, Montgomeryshire; Bala limestone of Coniston, 
N. Lancashire; ‘in olive shale of Coed Sion, Llangadoe, S. Wales. 
Explanation of Figures —P1. 1. H. fig. 38. Natural size of a variety with continuous wrinkles, from 
Llwyn-y-ci; fig. 39, variety with interrupted wrinkles from Llandeilo; fig. 39 a, superficial striee of ditto mag- 
nified ; fig. 39 4, profile of both valves; fig. 39 ¢, internal cast of rostral portion of receiving valve, shewing the 
dental lamellze, from Bryn Melyn, Bala. 
LEPTHNA LEVIGATA (Sow.) 
Ref. and Syn.—Sow. Sil. Syst. t. 13. f. 3. L. lepisma (Dalm. and Sow.) Salter in Mem. Geol. Surv. Vol. II. 
Part 1. t. 26. f. 3 and 4. (Not of Sow. Sil. Syst., and no such species described by Dalman). 
Sp. Ch.—Shell gibbous, transversely oblong, or fusiform; hinge-line a little exceeding the width of the 
shell, forming short, abruptly contracted, slender pointed ears; cardinal area very narrow, triangular; sides 
and front nearly smooth, marked with excessively fine lines of growth, and towards the margin with ex- 
tremely faint indications of very obtuse close ribs, separated by very narrow sulci, about nine in one line; 
margin forming a uniform short curve; surface fibrous, substance thick, with rather distant, very large 
punctures on the internal cast: internal cast of receiving valve with an ovate, tumid pair of muscular im- 
pressions, extending scarcely one-third the length of the shell, cleft by the very deep slit of a prominent 
mesial septum from the beak, slightly exceeding them in length: internal cast of entering valve rough, 
with large spinulose puncta, and with a strong mesial septum, extending two-thirds of the length of the 
shell. Width three lines, proportional length ;{;, depth of receiving valve ;, depth of entering valve °. 
The figures given in the Memoirs of ihe Geol. Survey, as above quoted under the name Leptena lepisma 
(Dal.) var. minor, with reference to t. 8. f. 7. of the Sil. Syst., certainly belong to this species, in which the 
faint broad strize are rarely to be found; and Mr Salter mentions that he doubts the distinction himself of 
the LZ. levigata. Further, I might mention, that there seems to be no such species as L. lepisma described 
in any of the works of Dalman; and the specimen so called by Sowerby I find agrees with Dudley specimens, 
which I have certainly determined to be the young of ZL. transversalis, on comparison with a number of 
Gothland specimens. 
Position and Locality—Not uncommon in the greenish mudstone of Clungunford, Shropshire; in the 
greenish schists at Keeper's Lodge, Goldengrove, Llandeilo, Caermarthenshire ; common in the schists of 
Mynydd-y-Gaer, Llanefydd. Denbighshire; in vast profusion in the decomposing schists of Dyffryn Castle, 
Devil’s Bridge, N. Wales; also thickly covering the surface of thin gritty flags at Gwyddelwern, Derwen, 
Denbighshire ; fine sandy flags near Welchpool, Montgomeryshire. 
LEPTHNA ? MINIMA (Sov.) 
Ref.—Sow. Sil. Syst. t. 13. f. 4. 
Sp. Ch.—Semicircular, or obscurely quadrate; hinge-line slightly exceeding the width of the shell, forming 
very short pointed ears; cardinal area large, triangular, about five times wider than high in the receiving 
HH2 
