462 
ELEMENTS OF GEOLOGY. 
Fig. 530. 
Lingula LeiHsii, J. 
Sow. Abberley 
Hills. 
the septuiti itself contains a small chamber, making five. 
The size of these septa is enormous compared with those of 
any other brachiopod shell; and they must nearly have di¬ 
vided the animal into two equal halves; but they are, nev¬ 
ertheless, of the same nature as the septa or plates which are 
found in the interior of Spirifera^ Terebratula^ and many oth¬ 
er shells of this order. Messrs. Murchison 
and De Verneuil discovered this species dis¬ 
persed in myriads through a white limestone 
of Tipper Silurian age, on the banks of the 
Is, on the eastern flank of the Urals in Rus¬ 
sia, and a similar species is frequent in 
Sweden. 
Three other abundant shells in tbe Ayme- 
stry limestone are, 1st, Lingula Lewisii (Fig. 
530) ; 2d, lihynohonella Wilsoni^ Sow. (Fig. 
531) , which is also common to the Lower 
Ludlow and Wenlock limestone; 3d, Atrypa 
reticularis^ Linn. (Fig. 532), which has a very 
wide range, being found in every part of the Upper Silurian 
system, and even Fig. ssi. 
ranging up into 
the Middle Devo¬ 
nian series. 
The Aymestry 
Limestone con¬ 
tains manv shells JRhynch^nella {Terebratula) Wilsoni, Sow. Aymestry. 
especially brachiopoda, corals, trilobites, and other fossils, 
amounting on the whole to 74 species, all except three or 
Fig. 532. four being com¬ 
mon to the beds 
either above or be¬ 
low. 
The Lower Lud¬ 
low Shale contains, 
^ among other fos¬ 
sils, many large 
cephalopoda not 
known in newer 
rocks, as the L/irag- 
moceras of Brode- 
rip^ and the Litu- 
Atrypa reticularis, Linn. {Terebratula affi,7iis, Min. Con.) ofBreyiliuS (see 
a. Upper valve, b. Lower valve, c. Anterior margin of Figs. 533, 534). 
the valves. latter is part¬ 
ly straight and partly convoluted in a very fiat spire. The 
