840 Report or tHE State GeoLocist. 
centric lines. Interior with a spondylium in each valve as in 
PARASTROPHIA; that of the pedicle-valve is the wider and is 
supported by a median septum near its anterior extremity. 
In the brachial valve the convergent plates generally rest 
upon the inner surface of the shell, though sometimes the 
spondylium is supported at its anterior extremity. The crural 
plates are extravagantly developed, forming two broad wing- 
shaped vertical expansions, concave on their outer surfaces ; 
their upper edges are curved over the hinge-line, their anterior 
edges broadly notched, and below this point appears the base 
of attachment for the crura; the walls of the spondylium 
being connected with them at the most convex point of their 
inner surfaces. The dental sockets are always small, and old 
shells frequently show a false foramen in the beak, which is 
simply an extension of the spondylium that does not appear 
to be accidental. The muscular impressions of this valve are 
frequently defined as a fourfold scar about the anterior end 
of the spondylium; in the pedicle-valve these impressions are 
rarely discernible. 
Type, Anastrophia Vernewili, Hall (Lower Helderberg). 
Distribution. Upper Silurian — Lower Devonian. 
Porambonites, Pander. 1830. 
(Plate 45, figs. 36-38.) 
Synonym; /sorhynchus, King, 1850. 
Shells robust, transverse or elongate, sometimes distinctly 
triangular and globose. Valves unequally convex, the brachial 
valve being always the deeper. FPedicle-valve with a sinus to 
which there is not always a corresponding fold on the opposite 
valve. Hinge-line straight; hinge-teeth very strong, resting on 
a broad hinge-plate. In both valves is a small obtusely triangular 
area, which is higher in the pedicle than in the brachial valve. 
Both valves with a broad pedicle-passage, never closed by a del- 
tidium. Sometimes the beak of the brachial valve is so strongly 
incurved that its perforation is not visible from outside. On the 
lateral slopes is a more or less strongly defined pseudolunule. 
In the interior of the pedicle-valve are two long, robust dental 
lamella which rapidly converge and unite, sometimes before the 
bottom of the valve is reached, then forming a low median 
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