Report of the 8ta til 1 



sions are elongate, and are partially inclosed i>\ the larger diduc- 



tors. The brachial valve lias a small 

 trilobed cardinal process, which is con- 

 tinued into a l«>w medial septum. The 

 muscular area is quadripartite and very 

 distinct. The brachial ridges are sharply 

 defined and appear to originate near the 

 outer extremities of the posterior adduc- wm.ma.- choneteiia .- 

 tors, making a broad outward, ami a more 



abrupt inward curve, completing one volution. Surface in the 

 pallia 1 region strongly papillose. 

 (Type, clmneteUa nasuta, Waagen. CFpper Carboniferous.) 



Chonopectus, Hall. 1892. 

 (Plate 20. Figs. 25-27.) 



Shells normally concavo-convex ; cardinal margin of pedicle- 

 valve with a row of spines. Beak of pedicle-valve compressed or 

 flattened from attachment in early growth. Internal markings 

 obscure. External surface reticulated by a double, oblique series 

 of concentric lines covering exceedingly line radiated striae. 



Type, Chonopectus JFtscheri, Xorwood and Pratten (sp.). 



Distribution. Lower Carboniferous. But a single species is 

 known. 



Strophalosia, King. 1SJ4. 

 (Plate 21, Figs. 1-11.) 



Shells productoid in general form; a cicatrix, usually apparent 

 on the umbo of the pedicle-valve, indicates that they were 

 attached to foreign bodies by the substance of the shell. Both 

 valves have a well-defined area and covered delthyrium, these 

 features being much the more conspicuous in the pedicle-valve. 

 In this valve the teeth are prominent, but not supported by 

 lamellae; the muscular arrangement is the same as in Pboductus, 

 though the diductor impressions are relatively larger and more 

 elongate, extending beyond the limits of the central adductois. 

 In the brachial valve the cardinal process is erect, bifid on its 

 anterior, and quadrifid on its posterior face. It is supported on 

 each side by short arched crural plates, and is continued into a 

 median septum which extends for half the length of the valve. 



163 



