LAMELLIBRANCHIATA. 343 



Pal^oneilo filosa. 



PLATE XLIX, FIGS. 33-38. 



NucidUes filosa, Conrad. Jour. Acad. Nat. Sci., Phila., vol. viii, p. 250, pi. 15, fig. 7. 1842. 

 PaUBoneUo filosa (Conrad), Hall. Prelim. Notice Lamellibranchiata, 2, p. 10. 1870. 



" " " " Pa-1. N. Y., vol. V, pt. 1. Plates and Explanations: PI. 49, figs. 33-38. 



1883. 



Shell below the medium size, elongate-ovate, or ovate-sub-cuneate in its shorter 

 varieties; length about twice the height in the prevailing forms. Basal 

 margin gently curving. Posterior extremity obliquely sub-truncate. Car- 

 dinal line arcuate ; anterior end regularly rounded. 



Valves depressed-convex in the lower part, becoming convex and some- 

 what gibbous in the middle and in the umbonal region. 



Beaks at about the anterior third, rising but little above the hinge-line. 

 Umbonal slope somewhat flattened. 



Surface marked, on the anterior half, by fine concentric striae, which pass 

 into sharp, elevated, lamellose striae on the posterior half. Interior shown 

 in figs. 36, 37 and 38 of plate xlix. 



Three specimens measure respectively 30, 25 and 23.5 mm. in length, and 

 15, 13 and 14 mm. in height. 



This species is closely allied to P. fecunda, of the Hamilton group, but is 

 readily distinguished by having the posterior extremity prolonged at the car- 

 dinal line, giving the greatest length at this point, while in that species the 

 greatest length of the shell is usually considerably below the cardinal line. 

 The shell is also smaller, seldom attaining much more than half the length of 

 P. fecunda. 



The prevailing forms, at the original localities, are proportionally longer than 

 that figured by Mr. Conrad, but there are among them forms of similar pro- 

 portions as in figs. 37 and 38. There being no other similar species known at 

 these localities, there can be no doubt of the propriety of this reference. 



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

 and Cortland, N. Y. 



