344 Thirty-fifth Keport on the State Museum. 



and the cast of the interior, a regular banded surface. These stronger 

 striae are closely arranged on the anterior side and ear, while on the 

 posterior side they preserve their equi-distant character. The right 

 valve is very distinctly marked by the elevated concentric striae. In 

 both valves there are radiating lines which apparently belong to the 

 structure of the shell. Interior unknown. Ligamental area nar- 

 row. 



One specimen has a length of 13 mm., height 16 mm., hinge-line 

 about 10 mm. Another example has a length of 12 mm., height 

 13 mm,, and hinge-line about 11 mm. 



The small size, erect ovate form, short hinge-line, the proportions 

 of height and length, and the surface characters, distinguish this 

 species from every other form here described. 



Formation and localities. In the soft shales of the Hamilton group, 

 shores of Oanandaigua lake, and at Norton's Landing, Cayuga lake, 

 N. Y. 



Leiopteria Oweni. 



Leiopteria Oweni, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: 

 PI. 20, fig. 10. Jan., 1883. 



Shell quite large, sub-rhomboidal ; body broadly ovate, oblique to 

 the hinge-line ; length greater than the height ; margins rounded, 

 produced posteriorly. Left valve convex, umbo gibbous, beak ele- 

 vated. Eight valve concave below, flat above, becoming convex to- 

 ward the beak, which is low and scarcely reaches the hinge. Hinge- 

 line straight, about equal to the length of the valve. Beaks an- 

 terior, acute, directed forward. Ear large, extended, defined by a 

 broad sulcus and marked byssal sinus. Wing large, expanded ; 

 margin concave ; extremity abruptly acute. 



Test thin, marked by fine concentric striae of growth, which on 

 some parts of the surface are crowded into fascicles, producing 

 ridges or undulations. These are somewhat regular over the whole 

 of the left valve, and stronger on the anterior part ; on the right 

 valve they are without regularity. The right valve also shows radi- 

 ating lines which appear to belong to the shell structure, and are 

 quite conspicuous in partially exfoliated specimens. The striae are 

 crowded and lamellose on the anterior margin and adjacent to the 

 byssal sinus; on the wing they are closely and evenly arranged. 



One of the imperfect specimens described has an approximate 

 length of 61 mm., height 55 mm., and hinge-line about 55 mm. ; 

 the measurement along the axis of the body, from the beak to the 

 post-basal margin, is 75 mm. 



