BRACHIOPODA. 845 
The pedicle-valve bears a short spondylium supported only at 
its posterior surface, the free extension being produced forward 
and upward into the cavity of the opposite valve; the crural 
plates of the brachial valve are concave on their outer surfaces 
and supported by convergent septa uniting as they reach the 
valve and leaving but asingle median line of union on its surface. 
Fria. 457. Fie 458. 
Fic. 457. Barrandella linguifera, Sowerby. Transverse section near’ the anterior extremity 
of the median septum in the pedicle-valve; showing the form of the spondylia, 
Fia. 458. Barrandella Barrandii, Billings. A transverse section in front of the termination of 
the median septun of the pedicle-valve; showing the form of the spondylium in 
both valves, and the coalescence of the septa in the (lower) brachial valve. 
Strong vascular, or ovarian sinuses radiate from the umbonal 
region of the pedicle-valve. These are complicated with the 
undefined diductor scars and are, therefore, to a certain extent, of 
muscular origin. 
Type, Barrandella linguifera, Sowerby (sp.). 
Distribution. Upper Silurian — Devonian (). 
Pentamerella, Hall. 1867. 
(Plate 48, figs. 6-15.) 
Shells with median fold and sinus as in Barranpexxa, usually 
larger and strongly plicate, possessing a very narrow cardinal 
area, an elongate pseudo-area, and incipient deltidial plates. 
The median septum on the interior of the pedicle-valve is very 
short, and at times is altogether absent. In the brachial valve 
the crural plates and supporting septa forma distinct spondylium 
which is broadly sessile on the surface of the valve. 
Type, Pentamerella arata, Conrad (sp.). 
Distribution. Devonian. 
Sieberella, Hhlert. 1887. 
(Plate 48, figs. 16-21.) f 
Galeatiform pentameroids having the median fold on the 
pedicle-valve and the median sinus on the brachial valve. Surface 
plicate without evidence of cardinal area or deltidial plates. 
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