PUPA. 201 



Linj^ual inonihranc with G-l rows of 21 (10 — 1 — 10) teeth; centrals with 

 three suboqual, very small cusps; laterals bieusi)i(l, marginals serrate, the inner 

 point much developed. 



This is a very variable species. The ordinary specimens vary chiefly in the 

 armature of the aperture, the marginal, internal rim of calcareous matter thick- 

 ening with age, and developing more numerous denticles. The Ohio speci- 



„, _„, mens arc of more than ordinary size, clean 



Fig. 104. ■ _ _ ■' ' 



and shining, and were the form designated 

 by Professor Adams as P. Tappaniana. 

 Those found in Massachusetts are consider- 

 ably smaller, covered with a well-developed 

 epidermis, and often, if not always, have the 



Lingual dentition of Pu;>rt/?<n/orfo». i -i 



aperture decidedly modified in form, being 

 more triangular, and the denticles more or less curved. To these was applied 

 the name curvidens ; and the modifications are so constant as to incline us still to 

 regard them as constituting a distinct species. With all its variations, it has an 

 aspect which enables us readily to separate it from all other species. The form 

 of the shell itself, and its semicircular aperture, are sufiiciently peculiar. A 

 more careful examination of the animal shows decidedly that it does not be- 

 long to Vertigo, as supposed by Mr. Say. 



Pupa decora, Gould. 

 Vol. ni. PL LXXI. Fig. 3. 

 Shell minute, cylindrical, rounded at apex, thin, shining, translucent, of a 

 wine-yellow color, regularly striated by lines of growth ; spire of 5 or 6 closely 

 revolving, rounded whorls, deeply separated at the sutures ; aperture nearly 

 round or semi-oval, obliquely limited by the penultimate whorl, armed with 4 

 slender denticles, the largest of them on the parietal wall, 1 on the columellar 

 portion of the peristome, and 2 on the outer portion, all disposed so as to form 

 the arms of a cross; the peristome is slightly reflexed, and indented opposite 

 the base of the two labial denticles ; at the columella it rises against a distinct 

 umbilical perforation. Length, 2.\ mill. ; diameter, 1^ mill. 

 Pupa decora, Gould, Proc, Bost. Soc. Nat. Hist., II. 263 (Dec, 1847), with a 

 woodcut; in Terr. Moll, II. 327, PI. LXXI. Fig. 3. — Pfeiffer, Mon. Hel. 

 Viv., III. 555. —W. G. BiNNEY, Terr. Moll., IV. 143; L. k Fr.-W. Sh., I. 

 238 (1868). —Gould and Binney, Inv. of Mass., ed. 2, 435 (1870). 

 Pupilla decora, Tryon, Am. Journ. Conch., III. 304 (1868). 



Near Lake Superior. Fort Resolution, Great Slave Lake. It thus appears 

 to be a species of the Xo.ihern Region. 

 Animal unobserved. 



Pupa corpulenta, Morse. 



Shell rimate perforate, elongate ovate, finely striated, polished, translucent, 

 dark olive-brown ; apex round, obtuse ; whorls 4, convex, tumid, wider at the 



