174. THE CHICAGO ACADEMY OF SCIENCES. 
GEOLOGICAL RANGE: Pleistocene. Loess. Otis Mull, Union 
County, South Dakota (Smith Coll.). 
Ecotocy: Probably the same as for typical columella; mud pool 
in old lime quarry (Lermond, Maine). 
RemMArKS: Chalybea is distinguished by its narrow shell, com- 
pressed acuminate spire, flattened body whorl and narrow and very 
effuse aperture. The excavated and arched columella is peculiar and 
will easily distinguish this variety from any form of typical columella. 
The spire is compressed and the aperture varies from elongate-ovate 
to expanded or even flaring. The columellar plait is very pronounced 
in this variety. The names included in the synonyms all seem minor 
variations of one form, although coarctata seems to stand midway be- 
tween chalybea and casta. Its peculiar columella seems to ally it rather 
with chalybea. Chalybea is not as narrow as casta, from which it is 
also distinguished by its deeply excavated and strongly arched colu- 
mella. In some localities the variety chalybea takes the place of typical 
columella. 
Pseudosuccinea columella casta (Lea). Plate XXIV, figures 
14-19. 
Lymnea casta LEA, Proc. Amer. Phil. Soc., II, p. 33, 1841; Trans. Amer. 
Phil SOCs ES, ppy lO din le44- Obs. IV ppalOn deleels4s. 
Lymnea casta WHEATLEY, Cat. U. S. Shells, p. 23, 1845——Morsr, Amer. 
Nat., III, pl. 11, fig. 15, 1870.—Scupper, Bull. Nat. Mus., 23, pp. 33, 43, 200, 1885. 
Limnea casta BINNEY, Check List, p. 12, 1860; Land & F. W. Sh. N. A., I], 
p. 26, fig. 43, 1865—Tryon, Con. Hald. Mon., p. 89 (63), pl. 16, fig. 3, 1872 
(figure not good).—Marsu, Conch. Ex., II, p. 110, 1887—-DEAn, Amer. Nat., 
XXVI; p. 11, 1892) 
Neristoma casta Tryon, Amer. Journ. Conch., I, p. 249, 1865. 
SHELL: Very elongate, somewhat fusiform, much compressed, 
inclining to obliquity; whorls 4-4™%, flat-sided and compressed; body 
whorl occupying from three-quarters to four-fifths the length of the 
shell; spire short, very acute, narrow; aperture strongly elongate- 
ovate, compressed in the center, the margins parallel in many speci- 
mens, rounded anteriorly and roundly angled posteriorly; it is some- 
what effuse anteriorly and occasionally a little expanded; inner lip 
straight in most examples, the lip somewhat erect, the columellar callus 
closely appressed to the parietal wall, but leaving, in most specimens, 
a small chink; axis gyrate. 
Length. Breadth. Aperturelength. Breadth. 
18.50 9.00 S  2250 5.10 mill. Type 
24.00 11.00 17.50 8.00 “ Bass Lake, Ind. 
20.50 10.50 14.00 200 les : re rr 
18.50 8.50 13.50 woo) - % < 
18.50 9.00 15.00 750 cu nce “ 
