44 PROCEEDINGS OF THE ACADEMY OF 



ment. It likewise differs from the existing species of Solenomya in having the 

 valves neatly closed all around, and the beak of its right valve curving under 

 that of the left. In this latter character, however, it agrees with the carbo- 

 niferous species of the West that have been referred to Solenomya, all of which 

 have the point of the right beak passing under that of the left, and Prof. 

 McCoy has noticed this character in British carboniferous species. These 

 carboniferous species, however, agree almost exactly in all their other known 

 characters with recent typical species of Solenomya, even to the general form 

 and the presence of an internal ridge under each beak, and differ as widely 

 from our shell in all respects, excepting in the one character of the slight 

 inequality of the beaks, as the recent species of Solenomya do. 



We are aware that Prof. King proposed to found a genus Janeia, for the 

 reception of the carboniferous and permian forms usually referred to Soleno- 

 mya, and afterwards abandoned it, after farther comparisons with recent 

 species. As he makes no allusion to the inequality of the beaks, it is proba- 

 ble he had no specimens of the fossil species with the two valves united. 

 From this character, and the greater excavation for the internal part of the 

 cartilage, under and extending a little in advance of the beaks, in the West- 

 ern carboniferous species referred to Solenomya, that we have had an oppor- 

 tunity to examine, we think it not improbable that the name Janeia may yet 

 have to be retained for the carboniferous and permian species, at least in a 

 subgeueric sense. Even in this case, however, it would still be necessary to 

 establish a new genus for our shell, in consequence of the differences already 

 noted, which separate it nearly as widely from the forms for which Janeia 

 were proposed as from the recent Solenomyie. 



It is proper to remark here, that some able conchologists, to whom we 

 showed specimens of the form under consideration, did not think it related 

 to Solenomya, as typified by the recent species, but more nearly allied to the 

 Anatinidse. As none of the numerous specimens of internal casts we have 

 had an opportunity to examine, however, showed any indications of a cavity 

 or process for the reception or attachment of an internal cartilage, as we see 

 in that family, and the pallial line has no traces of the sinus usually (though 

 not always) seen in the same, its relations to the Anatinidse seem to us 

 doubtful. 



Clinofistha radiata, var. levis. 



Edmondia ? radiala, Hall,(?) 1858. Iowa Geological Report, Vol. I, part 2, 



Palaeont., p. 716, pi. 29, fig. 3. 



Shell oval, approaching oblong, the height being from two-thirds to three- 

 fourths the length, moderately convex in young examples, and becoming ven- 

 tricose with age ; anterior side much longer and wider than the other, 

 regularly rounded in outline; posterior side very short, rather narrow below 

 the beaks, and vertically truncated; ventral margin most convex a little in 

 advance of the middle, thence round upward into the front, while behind the 

 middle, or nearly under the beaks, it is slightly contracted, or sinuous ; dorsal 

 outline subparallel to the base, the margins of the valves being erect anteri- 

 orly and rounding into the anterior margin; hinge line rather short ; beaks 

 rather ventricose, rising above the hinge line and placed about half way be- 

 tween the middle and the posterior end; posterior umbonal slopes often ren- 

 dered somewhat prominently rounded by a slight flattening of the valves 

 behind the beaks, near the truncated margin ; ligament lance-oval in form, 

 rather short, and placed immediately behind the beaks, exactly in the position 

 we would expect to see the lunule if the shorter side of the valves were the 

 anterior; surface with a polished appearance, and generally only showing fine 

 lines of growth, but in some examples also having obscure radiating marks 

 near the ventral margin, which are nearly always defined on internal casts. 



Length of a large specimen, 1 inch; height, 0-62 inch; convexity, 0-51 

 inch. 



[April, 



