326 SPIRIFERIDZ. 
and form two large curves facing the lateral portions of the 
valve; on approaching the front they form four or five conyo- 
lutions, which become smaller to the terminal coil, which faces the 
middle of the lateral portions of the shell; near the front the 
primary lamelle give off two processes which converge and 
extend between the spiral coils in an upward and backward 
direction; after becoming united towards the middle of the 
shell, they are again prolonged in the shape of a single lamella, 
which proceeds upwards for a little distance with its extremity 
directed towards the hinge-plate. In the interior of the ventral 
valve a mesial groove extends to about the middle of the shell, and 
on either side, running parallel with the hinge-line, are two broad, 
rounded projections, at the outer extremity of which is situated 
the articulating tooth; below these are the clevated muscular 
scars. 
HUNDELLA, Davidson, 1882. 
Distr —H. umbonella, Billings (cxxxvii, 15). Paleozoic ; 
Anticosti. 
Shell elongate ovate ; spiral cones with their apices directed 
towards the lateral margins of the shell; about six coils in each 
spiral; two principal stems of the spiral cones attached to the 
hinge- plate, and after extending a little way into the interior of 
the shell between the spirals, suddenly bent backwards towards 
the hinge; they then form a broad, rounded curve, facing the 
bottom of the dorsal valve, the curve being very gentle, so that 
the two primary lamelle on the dorsal side seem almost like 
parallel lines; when the primary lamelle reach the front they 
give off a semicircular band or loop having a projection or spike- 
like process at the top of it; this loop is directed upwards 
towards the beak, and is almost immediately behind the two 
primary lamellze on the dorsal side of the spirals; the loop is 
therefore internal to the spirals. 
Uncites, Defrance, 1826. 
Distr.—Fossil. Devonian; Europe. U. gryphus, Schloth. 
(exxxviii, 31, 32). 
Shell impunctate ; oval, biconvex, with a long incurved beak; 
foramen apical, closed at an early age; deltidium large, concave ; 
spiral processes directed outwards ; no hinge-area. 
The large, concave deltidium of Uncites so much resembles 
the channel formed by the dental plates of Pentamerus, that 
Dalman mistook the shell for a member of that genus. The 
discovery of internal spires, by Professor Beyrich, shows that 
it only differs from Retzia in being impunctate and destitute of 
hinge-area. Some of the specimens have corresponding depres- 
sions in the sides of the valves, forming pouches which do not 
communicate with the interior. 
