Bracwiopopa. | LOWER PALAZOZOIC MOLLUSGA. 249 
Selattyn Road, S. of Llangollen, Denbighshire; Bala schists of Alt Goch, Llanfyllin, Montgomeryshire ; 
Woolhope limestone of Littlehope; Bala schists of Rhiwargor, near Llanwddyn, Montgomeryshire ; abundant 
in the Caradoc sandstone of Acton Scott, Church Stretton, Shropshire; Bala sandstone of Alt yr Anker, Meifod, 
Montgomeryshire; ¢Bala limestone of Gaer Fawr, Welchpool, Montgomeryshire; Bala slates of Bwlch y 
Ciban; Upper Ludlow rock of Burton and Brocton, near Wenlock; fine sandstone of May Hill, Glouces- 
tershire. Var. y. Obscure specimens, possibly forming an extreme variety of this species, and seemingly refer- 
rible to the LZ. ptychotis (M°Coy), having the visceral disk semioval, and the wrinkles only distinct on the 
sides, occur in the Bala schists of Wilfa, Penmachno, N. Wales; Bala schists of Llanbedrog, W. of Pwllheli, 
Caernarvonshire ; Bala schists, Cefn Coedog, Corwen, Merionethshire; Bala schists of Cader Dinmael, near 
Corwen, Denbighshire. 
LertmNA (Leptagonia) uncuLA (M°Coy). Pl. 1. H. fig. 36 and 37. 
Ref.—Ild. M*Coy, Ann, Nat. Hist. 2nd Series, Vol. VIII. p. 404. 
Sp. Ch.—Semioval ; hinge-line as wide as the shell, forming short, rounded, slightly projecting ears ; cardinal 
area low, triangular, with a large tubular foramen at the apex of the beak; receiving valve horse-hoof shaped, 
from the slope of the deflected front being at a much more obtuse angle in the middle than at the sides; visceral 
disk depressed, very slightly convex towards the beak, rendered rugged by seven or eight large concentric wrinkles 
(only three or four at the margin commonly seen) ; angle between the disk and the deflected front obtusely 
rounded, the depth of the latter being rather less than the length of the disk; entering valve flat, concentrically 
wrinkled like the receiving one, but with a narrow margin, equally deflected all round, and only one-fifth or one- 
sixth the length of the disk ; surface of both valves radiated with extremely fine, close, obtuse, punctate strize, 
about twenty-eight or thirty-two, in two lines at four lines from the beak, (every third, fifth, or seventh of which are 
usually considerably stronger than the others in all the middle portion) : interior of both valves closely punctured 
and striate; the close, straight pallial impressions resemble the external strize on the deflected front, but are 
only eighteen in the space of two lines; interior of receiving valve with two rather long, very slightly curved 
dental lamellee, diverging at 105°, including the rotundato-trigonal pair of muscular impressions, which are 
one-third wider than long, and extend about half the length of the disk, being only separated by a slight 
indication of mesial septum at their anterior edge ; apex of the triangular boss of the foramen with a small, 
abrupt muero from the entrance of the matrix into the small tubular opening at the apex of the beak ; interior 
of entering valve with two very short diverging cardinal teeth, and a minute rostral tooth. Width eleven 
lines, proportional length 3%, length of disk in receiving valve =, length of disk in entering valve =, depth =. 
This so exactly resembles some of the small varieties of LZ. deltoidea and the L. camerata (Conrad), as 
figured by Hall, that I should not have thought of separating them, were it not for the very much finer striz, 
which very easily separate the species from our British specimens of L. deltoidea. The foramen of the apex 
of the beak is also larger, the dental lamellze more divergent, and the muscular impressions much wider. I find 
the peculiar hoof-like form and other characters of this little shell (unlike L. de/toidea) to be extremely constant. 
Position and Locality —Gregariously in extraordinary abundance, completely filling some beds of the 
Bala limestone of Llansantfraid, Glyn Ceiriog, 8. of Llangollen, Denbighshire; Bala limestone of Selattyn 
Road, S. of Llangollen, N. Wales. 
Sub-genus. CHONETES (Fischer).* 
Leprana (Chonetes) LATA (V. Buch. Sp.) 
Ref. and Syn.—Leptena lata V. Buch. Abhand. der Kon. Akad. for 1831, t.3, f.1, 2. Id. Sil, Syst. t. 5. f. 13. 
Sp. Ch—Transversely oblong ; hinge-line as wide as the shell; ears rectangular or slightly acute ; sides 
slightly convex, subparallel, or slightly converging ; front margin wide, subparallel with the hinge-line ; entering 
* See remarks on the genus Leptwna, page 233. 
[rasc. 11] Kx 
