238 BRITISH PALAZOZOIC FOSSILS. [ Bracniopopa. 
searcely one-third the length of the shell; anterior boundaries sharp, diverging at about 70°, enclosing between 
them a prominent semielliptical, mesial space, and narrowing the anterior ends of the muscular impressions, from 
each of which extend four or five thick diverging and dichotomising impressions of the pallial and ovarian 
vessels, a couple of similar dichotomising impressions on each side of the mesial space, and three or four 
very short ones on each lateral margin; the rest of the surface marked with obscure traces of the external 
stri, punctured in lines, the punctures becoming much larger at the margin between the branches of 
the pallial vessels; interior of entering valve concave for two-thirds the length from the beak, the margin 
abruptly arched over, very closely punctured (not in rows), and marked at the edge with numerous short 
simple ridges ; two very short cardinal teeth diverge from the rostral tooth; muscular impressions with very 
prominent boundaries all round, each one oblong, depressed, and nearly smooth in the middle, or subquadrate, 
slightly longer than wide ; the two together transversely oblong, one-third wider than long, the width equalling 
the length of the valve ; the two prominent inner boundaries leave a deep sulcus between them, at the anterior 
end of which only a very short mesial septum is developed, not reaching nearly to the beak; interior of 
the muscular impression nearly smooth, each divided by a faint diagonal ridge; the space immediately in front 
of the impressions coarsely pitted, and marked with a few obscure branching impressions of pallial vessels, none 
of which are visible on the deflected front; cardinal angles irregularly punctured, and with minute wrinkles. 
Width eight lines, proportional length of receiving valve =, of entering valve ;,, depth of entering valve 
2, depth of receiving valve 5%. 
This species is totally distinct from the L. transversalis in its much coarser strize, very much finer 
and more numerous punctures, and in the proportional width and concavity (instead of convexity) of the 
muscular impressions within their prominent boundaries. 
Position and Locality.—Greenish, sandy, Bala schists of Tan y Craig, Builth; Bala schists of Corwen, 
Merionethshire ; Bala schists W. of Llanfechan, Montgomeryshire; Bala schists of Moel Uchlas, Montgo- 
meryshire; Bala schists of Pen Cerrig Serth, Builth, Radnorshire ; extremely common in the Bala sandstone 
of Alt yr Anker, Meifod, Montgomeryshire ; common in the Bala schists of Cwm Lanerch, Bettws, N. Wales ; 
common in the Bala schists of Cricor Mawr, S. E. of Llanelidan, Denbighshire; Bala schists of Llansantfraid, 
Glyn Ceiriog, Denbighshire ; common in the Bala schists of Cefn Coedog, Corwen, N. Wales; Bala sandstone 
of Bodean, Pwllheli, Caernarvonshire ; common in the Bala schists and limestone of Rhosfawr, N. of Glog, 
Llanfyllin, N. Wales; in the Bala schists of Cefn y coed, Llangedwyn, Montgomeryshire ; a rather longer, 
extremely coarse variety, often an inch wide, extremely common, with the ordinary types, in the Bala schists 
of Gelli Grin, Bala, Merionethshire; impure Bala limestone of Goleugoed, Llandovery, S. Wales; Bala 
schists of Tan y Bwleh y groes, S. of Bala, Merionethshire ; abundant in the Caradoc sandstone of Horderly, 
W. and S.; Bala schists of Bryn Evan Yspatty, N. Wales; Bala limestone near Bryn Eithin, Penmachno, 
N. Wales; common in the calcareous Bala schists of Cader Dinmael, near Corwen, Denbighshire; Bala 
limestone of Tai yn y Nant, Bala; Bala schists of Milltir Cerrig, Llangynnog, Montgomeryshire ; Bala schists 
of Selattyn Road, S. of Llangollen, N. Wales; Bala schists of Peniarth Meifod, Montgomeryshire; very 
common in the Bala schists and limestone of Pont y Glyn Diffwys, W. of Corwen, Merionethshire ; very 
common in the Bala schists of Wilfa, near Penmachno, N. Wales; Bala schists S. of Llanfyllin, Montgo- 
meryshire ; Bala schists of Mathyrafal, S. of Meifod, Montgomeryshire ; sandstone of the Hollies, Church 
Stretton, Shropshire; Bala schists of Das Hithin ridge, Hirnant, Montgomeryshire ; sandy Bala schists of 
Pwllheli, Caernarvonshire ; Bala schists of Cyrn y brain, W. of Wrexham, Denbighshire ; in the Upper Bala 
limestone above Rother Bridge; Bala schists of Gaer Fawr, Montgomeryshire; Bala schists of Beaver’s 
Grove, Bettws-y-Coed, N. Wales; Bala schists and impure limestone of Pentre ewm dda, S. of Glyn Diffwys, 
N. Wales; schists of Penllys, W. of Meifod; ¢var. in Bala limestone of Coniston Water-Head, Lancashire ; 
var. spinangula common in Bala schists of Cwm of the Cymmerig, Bala; one doubtful specimen in the Bala 
schists of Tyn y cabled, Llanfyllin, N, Wales; var. in the Bala limestone of Craig Head, near Girvan, Ayrshire ; 
in the Bala rock of Alt Goch, Llanfyllin, Montgomeryshire; rare in the hard calcareous Bala schists of Capel 
Curig; Bala limestone of Horton in Ribblesdale, Yorkshire; greenish Caradoc sandstone, top of Moel Seisiog. 
