22 SIXTEENTH REPORT ON THE CABINET OF NAT, HISTORY. 



" LINGULA NUDA (n.s.)." 



Shell subelliptical j length nearly twice as great as the width ; 

 sides subparallel, very slightly curving, the greatest width near 

 the centre; base truncated; cardinal slopes rounded, the ventral 

 valve a little more pointed and more convex than the dorsal valve. 

 Dorsal valve nearly flat. Ventral valve, in exfoliated specimens, 

 marked by a depressed line down the centre, with indications of 

 foliate muscular impressions upon each side. 



Surface marked by fine concentric strise, which, on the margins, 

 are crowded and wrinkled. 



This shell resembles L. punctata in form, but is proportionally narrower : 

 it is truncate in front in the same manner ; the umbo is a little narrower, 

 and it has not the flattened space below the middle so distinctly indicated. 

 The surface marking, however, is always a more distinctive character. The 

 largest specimen examined, little exceeds half an inch in length. 



Geological formation and locality. In the shales of the Hamilton group, 

 associated with L. punctata : near Monteith's point, on Canandaigua lake. 



" LINGULA DENSA ( n. s.)." 



Shell subelliptical; sides almost exactly parallel for more than half 

 the length of the shell, abruptly curved at the basal angles, and 

 the base nearly straight or slightly curving; cardinal margins 

 gently curving. Middle and upper part of the shell prominent 

 and rounded; one valve ( ventral? ) showing a slight longitudinal 

 depression wdien exfoliated, \ni\\ fine wrinkled muscular impres- 

 sions. Valves somewhat abruptly flattened and compressed below 

 the middle. 



Shell comparatively thick, compact, and very closely and finely 

 striated concentrically with undulating strisBjthe exfoliated shells 

 showing radiating striae. 



This species has nearly the same form as L. punctata, but is more robust 

 and more abruptly elevated along the middle of the upper half of the valve : 

 the flattening is only near the lower extremity, and does not extend up- 

 wards in a triangular form as in that species. The absence of puncta, and 

 the close scarcely elevated fine strise, are distinguishing features. 



Geological formation and locality. In the upper part of the Hamilton 

 group, near Summit, Schoharie county ; occurring in large numbers in 

 some semi-arenaceous layers on the small stream flowing in a gorge known 

 as "Bear Gulf." 



" LINGULA DELIA (n.s.)." 

 Shell elliptical, twice as long as wide ; sides gently curving; base 



