Bracuiopopa. | LOWER PALZZXOZOIC MOLLUSCA. 255 
This species far exceeds the Lingula quadrata (Kichwald) in size, though that has hitherto been the 
largest species known ; it is easily distinguished therefrom, as well as from the Z. granulata (Phill.), to both of 
which it bears some resemblance, by the extremely minute granular lineation of the surface (which is quite 
invisible to the naked eye, or with a lens of low power only giving a dulness to the surface), and the semi- 
elliptical regular arch, formed by the union of the two posterior lateral margins of the shorter valve. In the 
ZL quadrata also the front is much rounded, and narrower; and the rather strong mesial lineation of the decor- 
ticated specimens does not occur.in our species, in which, when the surface is removed there are only seen 
traces of obsolete, broad, longitudinal, fibrous bands, not at all confined to the middle of the shell, nor linear 
in character. As usual in fossil Lingule, it is the beak only of the smaller valve which is seen most commonly ; 
but two of our specimens shew the pointed beak of the larger valve extending a quarter of an inch beyond the 
rostral margin of the other, the two being undisturbed from their original position. 
Position and Locality—Common in the sandy and calcareous Bala schists of Alt yr Anker, Meifod, 
Montgomeryshire ; sandy Bala schists of Das Eithin ridge, Hirnant, Montgomeryshire. 
Explanation of Figures —P1. 1. L. fig. 8. Natural size of short valve, with dotted restoration of beak of 
large valve ; fig. 8 a, view of beaks of both valves from another specimen ; fig. 8 4, transverse section of both valves 
about the middle ; fig. 8 c, longitudinal section of both valves, shewing the inequality of the beaks; fig. 8 d, 
surface magnified. 
Genus. SPONDYLOBOLUS (Af*Coy). 
Ref—Id. M°Coy, Ann. Nat. Hist. 2nd Series, Vol. VIII. p. 407. 
Gen. Char.—Suborbicular, slightly narrowed towards the indistinct, short hinge-line; nearly equivalve, 
flattened ; small valve with a slightly eccentric apex, beneath which, on the interior, the substance of the valve is 
thickened into a wide, undefined boss ; opposite valve slightly longer, from the apex being perfectly marginal, and 
slightly produced, channelled by a narrow, triangular groove below, the anterior end of which is flanked by two 
very prominent, thick, conical, shelly bosses, representing hinge-teeth : substance of the valves thick, testaceous, 
not glossy, minutely fibrous, but not distinctly punctured under a lens of moderate power, except by the ends of 
these fibres. 
One species of this genus is known already from the figures and descriptions of Mr Davidson, under 
the name Crania Sedgwickii, the prominent, cardinal protuberances being taken for the posterior pair of 
muscular impressions ; neither the tissue of the shell, nor the internal impressions have, however, any resem- 
blance to those of Ciania. The grooving of the beak of one valve, and the depressed orbicular form, shew 
the strongest affinity to the Russian genus, Obolus, which differs however by its glossy, corneous substance, 
peculiar internal impressions (as figured by Kutorga), and want of the conical cardinal bosses: these latter, as 
well as the terminal beak of one valve, and subcentral beak of the other, remind us of 7rematis of Sharp, but 
neither of the specimens I have examined of the small valve shew the fissure of that genus, nor does Mr 
Davidson allude to any thing of the sort in his large species ; and further, the coarse punctation of Trematis does 
not exist here. I think its zoological affinity very doubtful; the greatest affinity is probably with Siphonotreta, 
which it resembles very much if the tube in the beak be viewed as modified into a groove by a cleft or division 
of the internal rostral pad, the halves of which would thus correspond to the cardinal bosses of the present genus, 
forming a passage thus to Obolus. I think a peculiar family should be formed to include these three genera, 
the family being placed between Crania and Discina. 
SPONDYLOBOLUS CRANIOLARIS (A/*Coy). Pl. 1. H. fig. 4, 5. 
Ref.—Id. M°Coy, Ann. Nat. Hist. 2nd Series, Vol. VIII. p. 408. 
Sp. Ch.—Suborbicular, depressed, slightly undulated, the width scarcely exceeding the length; front and 
sides broadly rounded, slightly acuminated behind ; apex near the posterior margin ; substance of the shell thick, 
caleareous, smooth, with very minute, faint, concentric strie, very minutely fibrous, but the punctation (if it 
exists) indistinct : beak of small valve small, obtusely pointed, at about one-fourth the length from the posterior 
