124 DEVONIAN FAUNA. 
larger and more convex, and must be regarded as the beak; and hence these 
fossils are distinguished from the two forms previously described from Devonshire 
by having the fold on the dorsal instead of the ventral valve. 
(2) There are two larger but imperfect specimens, which seem to have more 
unequal apices, but to agree with the former set in having the fold on the dorsal 
valve. They appear very similar to Maurer’s types. The dorsal valve is seen to 
be very much swollen, and to be almost angular transversely and very convex 
longitudinally. The character of the sinus is the same as in Maurer’s figures. 
It seemed to me that both these forms should be referred to Maurer’s species, 
and I am confirmed in my view by finding some specimens of intermediate size and 
characters in the Woodwardian Museum. 
The beaks of the young form are generally much more equal than in the German 
shell, but as the beaks of small specimens of P. brevirostris are sometimes nearly 
equal I do not think much weight can be given to this character. 
2. Genus.—Concuipium, Linné, 1760. 
Gypipia, Dalman, 1828. 
Beak elongate, slightly recurved. Dorsal valve having separate excentric 
and diverging septa, bearing the crura; ventral valve as in Pentamerus. 
1. CoNCHIDIUM BRITANNICUM, n. sp. Pl. XIV, figs. 9, 9a, 9 0. 
Description.—Shell small, gibbous, very inequivalved. Ventral valve convex, 
inversely cordate, regularly arching from the beak to the front. Beak extremely 
elevated, slightly incurved, flattened. Apex sharp, very distant. Fissure large, 
broad, triangular, apparently bordered by a short area. Cardinal slopes broad, 
slightly concave. Ventral valve slightly channelled on the back by a small narrow 
sinus which extends from the beak to the front margin, and obliquely flattened on 
each side. Front margin concave in the centre and convex on each side. Surface 
covered with very numerous fine, sharp, irregularly alternating, distant and 
divaricating, elevated rays, which are also seen on the sides of the beak, and 
which are more than fifty in number. Structure massive. 
Size of ventral valve: height, 14 mm.; width, 16 mm.; depth, 7 mm. 
Locality.x—A single specimen of the ventral valve from Lummaton is in my 
Collection. 
