DAVIDSON — ON SOME FOSSIL BRACHIOPODA. 463 



Rhynchonella, 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 lamellse, 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 are 

 strongly marked in the interior of the smaller valve. 

 IP. 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 ^j^irif&ra, nor perpendicular as in 

 Atrypa, It differs from that otiKonincUna 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. lu the interior of the large valve the mus» 



