JURASSIC SPECIES. 137 



form and the distinctness of its costse, though our figure on plate 12 gives a 

 good idea of the most usual appearance of this shell. 



Locality avd position. — Weber Canon, Wasatch Range, Utah; Jurassic. 



Myaoites iNCONSPicuus, Meek. 

 Plato 12, fig. 10. 



Shell very small, depressed, elongate-subelliptic, moderately convex; 

 posterior margin narrowly rounded; anterior very short, truncated obliquely 

 forward from the beaks above, and rounded below; basal margin, subpar- 

 allel to the dorsal, most convex in outline at or slightly behind the middle, 

 and a faintly sinuous anteriorly; dorsal outline nearly straight, and horizontal 

 behind the beaks, but rourfding off very gradually posteriorly; beaks some- 

 what tumid, rising slightly above the cardinal margin just behind them, and 

 placed near the anterior end; posterior umbonal slopes prominently rounded; 

 while a broad shallow compression, or slight concavity, extends from the 

 beaks to the anterior ventral margin of each valve. Surface only showing 

 obscure concentric marks of growth. 



Length, about 0.45 inch; height, 0.20 inch. 



Although there is nothing particularly notable in the form or general 

 appearance of this little shell, I have been unable to identify it with any of 

 the described species. Perhaps its most marked features are its small size, 

 depressed form, and narrowly- rounded extremities. It may be a young 

 shell, and in larger individuals, more nearly approaching some of the described 

 species; but my present impression is that it is new. 



Locality and position. — Weber Canon, Wasatch Eange, Utah. The 



specimen was supposed to have come from the rock in which the Spiriferina 



and Aviculopecten of the same plate were obtained; but it probably belonged 



to some Jurassic bed at that locality. (See note on the explanations of 



plate 12.) 



Myacites (Pleuromya) Weberensis, Meek. 



Plate 12, figs. 11, 11 a. 



Shell of about medium size, moderately gibbous, subovate; anterior 

 side very short and subtruncated, but rounding into the base; basal margin 

 forming a semiovate curve, more prominent anteriorly, and curving up more 



