311 



Bulletin 5 41 



FOSSIL SHELLS. 135 



Description. Shell rounded, much compressed ; 

 the whole surface covered with scaly striae : ribs 

 elevated, rounded, with about three striae on the 

 back of each ; intervening grooves rather profound : 

 ears equal, sinus of the ear of the superior valve^ 

 profound, extending at least one third of the length* 

 of the ear. 



Length rather more than four inches and a half ; 

 breadth four inches and four-fifths. 



In magnitude this shell is justly entitled to com- 

 pare with the preceding ; but it differs in being 

 much less convex, and in having a much more 

 profound sinus in the ear of the superior valve. 

 Three specimens, from which the above descrip- 

 tion was taken, belong to the Academy, and were 

 presented by Mr. Watson. 



3. P. Clintonius.'^ PI. ix. fig. 2. Auricles equal ; 

 surface with from one hundred and forty to one 

 hundred and eighty elevated longitudinal lines. 



Description. Shell suborbicular, compressed, 

 with very numerous, regular, elevated striae, which 

 are muricated with minute scale formed by trans- 

 verse wrinkles, that are sparse in the middle of 

 the length, and crowded each side of the shell ; the 

 intervening spaces are regularly concave, and in 

 parts very distinctly wrinkled : auricles equal, 



* Mr. Finch requested that three species of his collection 

 that might prove to be new, should be dedicated to the dis- 

 tinguished men whose names these shells bear. 

 [J. A. N. S., Phila., ist Ser., Vol. IV, 1824.] 



