INVERTEBRATE PALAEONTOLOGY. 109 



Toldia in icrodonta, Meek. 



Plate 2, fig. 2. 



Toldia microdonta, Meek (1872), Hayden's Sixth Report United States Geological Survey of the Terri- 

 tories, 304. 



Shell small, longitudinally subovate, rather compressed; anterior margin 

 more or less narrowly rounded, being generally more prominent above the 

 middle; pallial margin forming a semi-ovate curve, being more prominent 

 before than behind the middle, and curving up gradually and obliquely at 

 both ends; posterior side compressed, and with its margin narrowly rounded, 

 or almost subangular at its connection with the hinge above; cardinal margin 

 sloping gradually from the beaks, the posterior slope being very slightly con- 

 cave in outline, and the anterior nearly straight; beaks rather depressed and 

 placed a little in advance of the middle; hinge-line equaling about three- 

 fourths the entire length, and provided with very fine, regular, pointed 

 denticles, of which twenty-six may be counted behind, and twenty before the 

 beaks, in each valve. Muscular and pallial impressions very obscure, and 

 not visible on internal casts. Surface not well known. 



Length, 0.50 inch; height, 0.28 inch; convexity, 0.14 inch. 

 In general outline, and the nearly central positions of its beaks, this shell 

 bears some relation to Yoldia bisulcata, M. and H., from the Fox Hills group 

 of the Upper Missouri Cretaceous ; but it is a very decidedly more compressed 

 species, and, judging from impressions left in the matrix, it was evidently less 

 strongly striated. Indeed, it seems to have been nearly smooth, in which 

 character, as well as in some other respects, it is probably more nearly related 

 to Y. Evansi, M. & H., from which it differs in being proportionally shorter, 

 higher, and more compressed. Among European species, it is represented 

 by such forms as Yoldia scapha (Nucula scapha, d'Orbigny, Paleeont. of France, 

 III, pi. 301, figs. 1-3), from which it also differs in being more compressed, 

 with the posterior side wider, and the posterior dorsal slope distinctly less 

 concave in outline. 



Locality and position. — Twelve miles southwest of Salina, Kansas; from 

 a brown sandstone of the age of the Dakota group of the Upper Missouri 

 Cretaceous. Discovered by Professor Mudge, of the Kansas Agricultural 

 College. 



