24 



foundly impressed: spire rather prominent and acute: apcrlurr 

 ovate; the superior termination rounded* 



Inhabits margins of ponds near New Harmony. 



This species is remarkable for the very deep indentation of 

 its suture, giving to the whirls of the spire the appearance of 

 being almost separated from resting on each other; and by this 

 character it may be readily distinguished from the other spe- 

 cies of this country. It was found by Dr. Troost. 



S. undulala* Shell suboval, pale yellowish, translucent, fra- 

 gile: volutions three and a half: spire moderate, wrinkles ob- 

 solete; body whirl wrinkled, or rather slightly undulated: co- 

 lumella narrowed, so as to exhibit the appearance of an inte- 

 rior umbilicus when viewed with a lens from the base. 



Length, about half an inch. Inhabits Mexico. 



Very similar to S. ovalis. Nob., but the suture is not so 

 deeply indented, and it has from one-half to three-fourths of a 

 whirl more; the surface of the body whirl, also, is rather un- 

 dulated than wrinkled. One of the individuals lived nearly 

 twelve months in my cabinet without any apparent sustenance. 



PUPA, Lam. 



P. placida. Shell dextral, cylindric conic, pale yellowish 

 horn color: apex whitish, obtuse: whirls six and an half, some- 

 what wrinkled: suture moderately impressed; ap<rturc unarm- 

 ed, longitudinally oval, truncate a little obliquely above by 

 the penultimate volution: columella, so recurved as almost to 

 conceal the umbilicus: labrum, with exception of the superior 

 portion, appearing a little recurved when viewed in front, but 

 when viewed in profile this recurvature is hardly perceptible: 

 umbilicus very narrow. 



Length, over three-tenths of an inch. Inhab. Massachusetts. 



For this shell I am indebted to Dr. T. W. Harris, of Milton, 

 from whom I have received many interesting species of our 

 more northern regions. At first view it might be mistaken for 

 the P. margiaala, Nob., but it is quadruple, the size, and the 

 labrum is not reflected and thickened. 



