334 PALEONTOLOGY OF NEW YORK. 



It is proportionally much higher than P. plana and smaller and more constricted 

 than P. maxima. 



Formations and localities. In the shales of the Hamilton group, Fultonham 

 and Bear's gulf, Schoharie county; shores of Seneca and Cayuga lakes, N. Y., 

 and Patterson's creek, Va. ; in the Portjige group, at Portland Harbor, Chautau- 

 qua coimty, and in the lower Chemung or Ithaca group, at Ithaca, N. Y. 



Pal^oneilo constbicta, yar. flexuosa. 



PLATE XLVIII, FIGS. 17-20. 



PalfBoneilo constricta (CoMBADsp.), tjar. flexuoxa. Ham,. Pal. N. Y., vol. v, jit. I. Plates and Explanations : 



PI. 48, tigs. 16-20 (16 in error). 18S3. 



Specimens having the general aspect of P. constricta occur in the Chemung 

 group, at Ithaca. The shell is stronger, more elongate in form, more coarsely 

 and irregularly striated with the constriction at the posterior end strongly 

 marked. 



Formation and locality. In the lower part of the Chemung group, at Ithaca, 



N. Y. 



Pal^eoneilo plana. 



PLATE XLVUI, FIGS. 21-28. 



PalcBoneilo plaTta, Hall. Prelim. Notice Lainellibranchiata, 2, p. 7. 1870. 



" " Pal. N. Y., vol. .5, pt. 1. Plates and Explanations : PI. 48, figs. 21-28. 1883. 



Shell below the medium size, transversely elliptical, compressed, elongate and 

 somewhat pointed behind ; length almost twice the height ; basal margin 

 regularly and gently rounded, with a slight and undefined constriction near 

 the posterior end. Posterior extremity acutely rounded. Cardinal line 

 declining on each side of the beak. Anterior end regularly rounded. 



Valves depressed-convex. 



Beaks anterior to the centre, small, rising but little above the hinge-line. 

 Umbonal slope not defined, obscurely indicated by an undefined depression, 

 which scarcely constricts the margin. 



Surface marked by very fine concentric striae, which are often obscure or 

 obsolete. Interior as shown in figs. 25, 26 of plate xlviii. 



Several specimens have a length of 15 mm. and a height of 8 mm. 



