DAVIDSON — ON SOME FOSSIL BRACHIOPODA. 
463 
Rhjnchonella, and other of the articulated genera. In the interior of 
the dorsal valve there exists no distinct hinge-plate, but socket-ridges are 
wide, and to these are fixed two small cylindrical stems, which soon 
become converted into two broad spiral lamellae, which form large ver- 
tical hollow cones, closely adpressed, with their extremities directed 
inwards towards the centre of the valve ; in the interior of the valve 
quadrupled impressions of the adductor, or anterior and posterior oc- 
clusor muscle, are separated by a medio-longitudinal ridge ; but all these 
and other internal characters will be more clearly understood by a glance 
at the illustrations we have given, than by the most elaborate de- 
scription. 
The genus Koninckina was established by Mr. Suess for the reception 
of a remarkable shell which had for long been considered as a species 
of Productus. The shell is concavo-convex, and considerably adpressed, 
the beak of the ventral valve rather large and incurved ; no articulation 
has been hitherto discovered. The smaller or dorsal valve is concave 
exteriorly, convex interiorly, and the oral arms were supported by two 
slender spiral lamellae, forming four widely-separated convolutions 
directed inwards, and almost horizontal with the bottom of the valve. 
No muscular scars have been detected, but the vascular impressions arc 
strongly marked in the interior of the smaller valve. 
The genus Anoplotheca was proposed by Dr. Sandberger for a shell 
which the author considered to be closely related to Koninckina, but 
differing in several particulars ; it is concavo-convex, with neither area 
nor deltidium. The attachment of the spiral appendages is but imper- 
fectly known ; they are formed of about ten whorls, the base of the 
spiral coil being inclined at an acute angle on the median level of the 
shell, but is not parallel to it, as in Spirifera, nor perpendicular as in 
Atrypa. It differs from that oiKoninclcina by the greater number of con- 
volutions. In the interior of the smaller or dorsal valve there exists no 
hinge-plate, but the sockets for the reception of the teeth of the oppo- 
site valve are unusually large and deep, and between these there exists 
a prominent peculiarly-shaped cardinal process, and under it may 
be seen a small oval depression, bordered by an elevated rim ; but the 
use of this depression has not been hitherto explained ; besides these, 
the quadruple impressions left by the adductor or posterior and anterior 
occlusors are divided by a mesial ridge, which fills up a large portion of 
the bottom of the shell. In the interior of the large valve the mus- 
