WAVEELY GROUP SPECIES. 303 



Grammysia, and have concluded to place it provisionally in that group, 

 until its relations can be more precisely determined from the study of 

 better specimens. 



Locality and position : Same as last. 



GrRAMMYSIA VENTRICOSA, Meek. 



Plate 16, figs. 6n, 6 (and pi. 13, figs. 5a, h, var.) 



Grammysia ventricosa, Meek (1871); Proceed. Acad. Nat. Sci., Philad., XXIII., 73. 



Shell attaining a moderate size, extremely ventricose, the convexity 

 being greater than the height, with the greatest gibbosity a little in 

 front of and above the middle ; height equaling about half the length ; 

 posterior side comparatively long, a little gaping and narrowly rounded 

 in outline at or a little above the middle ; pallial margin usually slightly 

 sinuous near the middle, or in front of it ; anterior side very short, con- 

 cave just under the beaks to the base of the lunule, where the margin is 

 subangular, or very abruptly rounded and most prominent, while below 

 this it curves obliquely backward into the base; cardinal margins 

 scarcely more than equaling half the entire length of the valves, and 

 inflected so as to form the usual shallow escutcheon ; beaks very gibbous, 

 moderately elevated, oblique, strongly incurved, and placed almost over 

 the anterior margin; lunule deep, ovate or obovate, and well defined; 

 posterior umbonal slopes prominently rounded; flanks without any 

 oblique ridge or sulcus. Surface marked on the anterior side of the 

 valves, near the lunule, by small wrinkles, which pass into mere lines 

 and linear furrows of growth farther back, while even the latter become 

 nearly or quite obsolete over the more gibbous parts of the valve. 



Length of largest specimen seen, 2.50 inches ; height, 1.30 inches ; con- 

 vexity, 1.55 inches. 



I know nothing of the hinge or muscular and pallial impressions of 

 this shell, and refer it, like the last, to Grammysia, from its form and 

 general appearance. It shows no traces of the oblique ridge and furrows 

 seen on the typical species of that genus, but it is well known that this 

 character is not constant in the group. 



Locality and position Same as foregoing. 



