JURASSIC SPECIES. 137 



foi-ni and tlie distinctness of its costa?, though our figure on plate 12 gives a 

 good idea of tlie most usual appearance of this shell. 



Localitij and position. — Weber Canon, "Wasatch Range, Utah; Jurassic. 



Myacites iNCONSPicuus, Meek. 

 Plato I'2, 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 fixintly sinuous anteriorly; dorsal outline nearly straight, and horizontal 

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

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

 l)laced 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 rjange, Utah. The 

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

 and Avicvlopeden of the same plate were obtained; Init it probably l)elonged 

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

 plate 12.) 



Myacites (Pleuromya) Webebensis, Meek. 



Plato la, figs. 11, llrt. 



Shell of a1)out medium size, moderately giljbous, sul)ovate; anterior 

 side ^•el•y short and subtruncated, but rounding into the base; basal margin 

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



