TO PROCEEDINGS OF THE ACADEMY OF 



show faint traces of two or three very obscure longitudinal ridges 

 above the umbonal angle of each valve, and impressions in casts, 

 of a slight ridge behind the anterior muscular impression, that are 

 not seen in our shell. 



From the little that is now known of the shell that will pro- 

 bably have to be regarded as the type of the genus Sanguinolites, 

 it is impossible to determine whether or not such shells as this 

 can be properly referred to that genus. They seem to agree, how- 

 ever, more nearly with the same than they do with the typical 

 forms of AUorisma, to which they are also related. 



Locality and position. Rushville, and Newark, Ohio. Upper 

 part of the Waverley group, of the lower Carboniferous. 



ALLORISMA (SEDGWICKIA?) PLEUROPISTHA, Meek. 



Shell depressed and elongated, or more than twice as long- 

 as high, moderately convex centrally and anteriorly, and alate 

 and produced behind ; pallial margin long, nearly straight along 

 the middle, rounded up anteriorly and ascending more gradually 

 behind ; posterior side very narrow, truncated and somewhat 

 gaping at the extremity, which intersects the cardinal margin at 

 an obtuse angle, and rounds abruptly into the base ; anterior side 

 wider (higher) than the other, and more or less abruptly rounded. 

 Dorsal margin depressed below the horizon of the beaks behind 

 the latter, where it is concave or nearly straight in outline, and 

 inflected so as to form a short corselet near the beaks ; while in 

 front of them it slopes forward rather abruptly, and is provided 

 with a well-defined oval lunule. Beaks moderately prominent, 

 rather gibbous, and incurved without any obliquity or fissure; 

 placed a little less than one-third the length of the valves from 

 the anterior margin. Posterior umbonal slopes subangular, the 

 ridge extending toward the posterior basal extremity, but becom- 

 ing obsolete before reaching it ; while above this ridge the poste- 

 rior dorsal region is flattened or a little concave and smooth. 



Surface oi*nated with more or less defined concentric wrinkles 

 and lines of growth, which are crossed on the posterior portions 

 by linear but distinct raised radiating costse, separated by wider 

 depressions. Of these costa?, the anterior ones descend almost 

 verticall}^ from the beaks to the base ; while farther back they 

 gradually become more oblique, and near the middle of the flanks 



[June 6, 



