288 REPORT ON THE STATE CABINET. 



having narrow hinge-areas and small teeth and sockets, with reniform 

 vascular impressions of the form of those illustrated, the name Pro- 



DUCTELLA. 



Subgenus Produotella, n.s-g. — Shells having the general form of Pro- 

 DUCTUS, but uniformly with a narrow area on each valve, a foramen 

 or callosity on the ventral area,* small teeth, and more or less 

 distinct teeth-sockets. 



The reniform vascular impression, rising from between the anterior 

 and posterior occlusor muscular impressions, curves gently outwards, and, 

 following a curvature somewhat parallel with the margin of the shell to 

 below the middle of its length, is abruptly recurved, and the extremity, 

 turned a little backwards, tei-minates about half way between the margin 

 and the anterior extremity of the mesial septum. 



The cardinal process, seen from the inner side, is bilobed, and from 

 the exterior side each of these divisions is usually bilobed. 



These shells difl'er from Strophalosia in the extremely narrow linear 

 cardinal area, greater extension of the hinge-line, more extreme arcuation 

 or ventricosity of the ventral valve in many or most of the species, and 

 especially in the direction and termination of the reniform vascular 

 impressions, which resemble those of Aulosteges and of some species of 

 Productus. They differs from the typical forms of Productus in the 

 constant presence of an area, hinge-teeth and sockets. 



* In the specimens affording the most satisfactory evidence of area, etc., the foramen is open ; 

 but in some specimens the impression only remains, and there is the appearance of a narrow 

 indentation below the beak, so that it is impossible to determine whether the foramen has been 

 open, or closed by a deltidium. 



