254 BRITISH PALAZOZOIC FOSSILS. [Bracutopopa. 
the front margin, which is broadly rounded ; greatest width about one-third of the length behind the front 
margin ; sides slightly convex, gradually converging behind to the obtuse beaks; rather abruptly compressed at 
the sides of the posterior half of the shell; surface black, glossy, and nearly smooth to the naked eye, marked 
under the lens with sharp, irregular, minute, concentric lines, crossed by exceedingly fine, nearly obsolete, longi- 
tudinal strize. Length seven lines, proportional width =;, depth of both valves about =. 
This species seems perfectly identical in all characters with the Trenton limestone species, to which I refer 
it, and differs from Sowerby’s measurement and figure of his L. attenuata in the greater proportional width, as 
well as much less acuminate, posterior end. 
Position and Locality—Llandeilo flag (Bala rock) of Llandeilo, Caermarthenshire. 
LiIncuLA ovata (M°Coy). Pl. 1. L. fig. 6. 
Ref.—M°Coy, Synop. Silurian Fossils of Ireland, p. 24. t. 3. f. 1. 
Sp. Ch.—Elongate, ovate, gently convex along the middle, gradually compressed towards the margins ; 
greatest depth about the middle of the length ; sides nearly parallel, very slightly convex ; greatest width about 
the middle of the length; front scarcely narrowed, obtusely rounded, nearly straight ; sides merging gradually 
into the slightly convex posterior lateral margins, which unite in a narrow elliptical point at the beak, forming 
an angle of about 60° in the long and 80° in the short valve; substance of the shell very thin, marked with 
delicate, close, irregular concentric plications of growth, the middle portion being occupied by fine, parallel, 
longitudinal strize, strongest at the margin, those at the sides turning outwards nearly at right angles to the 
lateral margins, where alone they are visible, (about twelve in the space of one line) ; mesial ridge separating 
the muscular impressions, apparently rather less than half the length of the shell. Length one inch three lines, 
proportional width 4 to “ (most commonly the former in the long valve, the latter in the short valve, thus 
diminishing the amount of variation), depth about ;;. 
This beautiful species is remarkable for its large size, slender depressed form, and delicate longitudinal 
lineation. I can add nothing of importance to my original description, in which I pointed out its differences 
from the L. Lewisi and L. attenuata, &c. which it is scarcely necessary to do now. 
Position and Locality.—Oceurs in considerable abundance in the fine green Lingula slates, S. of Penmorfa, 
Tremadoe, N. Wales, along with the more abundant L. Davisi (M°Coy), from which it differs in its great size 
and slender form (age producing the opposite change of proportions in the Lingulw), and the delicate longitu- 
dinal striation under the lens; common in the Lingula slates of Festiniog, N. Wales; rare in the Coniston 
(Bala) limestone of Coniston, Lancashire ; one doubtful specimen in the Bala schists of Bryn Melyn, near Bala, 
Merionethshire. 
Explanation of Figures.—P1. 1. L. fig. 6. Natural size, from slates South of Penmorfa ; fig. 6 a, section 
about the middle. 
LINGULA TENUIGRANULATA (J/*Coy). PI. 1. L. fig. 8. 
Ref—Id. Ann, Nat. Hist. 2nd Series, Vol. VIII. p. 406. 
Sp. Ch.—Shell black, semielliptical, sides parallel, abruptly rounded to the wide, nearly straight front, 
gradually rounding into the undefined, arched, posterior, lateral margins, which unite elliptically in front of the 
beak, the curve being rather wider than a semicircle, in the small valve, more elongate from the projection of the 
considerably longer beak in the opposite one; valves with a moderate, flattened, triangular gibbosity, widening 
from the beak to the front, from which the sides slope rather abruptly to the margins, the greatest depth 
being at about the middle of the length ; surface with irregular, flattened, concentric laminar wrinkles, strongest 
on the sides, nearly obsolete in the middle; entire surface covered with extremely minute, close, regular, equal, 
sharply granular, longitudinal, slightly undulated strize (about twenty-six in one line in the middle of the shell), 
the intervening spaces between the strize about equalling the strie in width. Length (of shorter valve) one 
inch nine lines, proportional width ©, depth = 
1009 Too * 
