11 



preaching more nearly to the latter in form and color. In 

 adult specimens I have never found any variation in the num- 

 ber or situation of the teeth. At a little distance back of the 

 outer lip, and answering to the two teeth within, are seen two 

 indentations, showing that the parts within are folds rather 

 than teeth ; and this is very plainly seen to be the case in 

 young specimens. Its length is about ^ inch, breadth 2 \ inch. 

 It was first sent to me by Dr. W. Newcomb, of Troy, N. Y., 

 and subsequently by Prof. E. Foreman, from Baltimore and 

 Worcester County, Md. Since then I have found it, in August, 

 upon sticks and about the roots of trees in the woods in Cam- 

 bridge and Roxbury. It seems to be abundant. 



PUPA PENTODON. 



Plate XVI. fig. 10. 11. 



P. ovato-oblonga, albida, umbilicata ; anfractibus quinque, convexis, apice subacu- 

 ta; apertura oblique semiovata, dentibus 5-8 instructs*, quorum 1-2 postic, 2 ad col- 

 umellam, 2-5 ad labrum positis ; labro expanse. 



" Shell dextral, subovate, whitish horn-color ; apex obtuse ; 

 whorls five, glabrous, convex ; suture not very deeply im- 

 pressed ; aperture semioval ; labrum two-toothed, of which a 

 single very prominent one is on the middle of the transverse 

 labium, and the other remote, much smaller, and placed on 

 the basal angle of the columella ; labrum regularly arcuated, 

 tridentate, tooth nearest the base very small and placed near 

 the smaller tooth of the columella ; the two others larger, sub- 

 equal ; umbilicus distinct. Length less than ^ inch. 



Lower tooth of the labrum sometimes obsolete. 



Animal, foot white, head and neck, as far as the mantle, 

 black." (SAY, Journ. Acad. Nat. Sc. II. 376.) 



This is the most variable of all our species. While there 

 is no doubt as to this being the shell intended by Mr. Say as 

 his pentodon, it is unfortunate that he should have selected so 

 inappropriate a name, inasmuch as the shell is never found 

 with five teeth except in an immature state, when the number 

 is even reduced to four. It is nevertheless true that five of 

 the teeth are constant, viz. : one upon the transverse lip, two 



