In the 1850 Census, there is no question that the census-taker wrote "Lucinda" for the 2-year-old child and that no "Leander" was listed.  I'm not sure where the error lies here.

1.  Census Index:  U.S. Selected Counties, 1830 (Broderbund CD-315):  not found, as expected.

2.  Census Index:  U.S. Selected Counties, 1840 (Broderbund CD-316):

1840

Lias, Jacob

PA

Armstrong Co.

Wayne Twp.

p. 19

3.  1850 Census Index/Microfilm (online at GenealogyLibrary.com):  Cownshanock Twp., Armstrong Co., PA, p. 228B, 128/130, enumerated 6 Sep 1850 (extracted by Diana Gale Matthiesen):

Jacob Lias	49	M	Farmer	2000	Pa
Susannah "	37	F			"
James    "	14	M			"
McKindria "	13	M			"
Eliza    "	7	F			"
Asbery   "	5	M			"
Elizada  "	4	F			"
Lucinda  "	2	F			"

Jacob's birth and death dates above are said to be from his tombstone and death certificate, so the census-taker appears to be in error, that is, Jacob should be 39, not 49.  The mistake seem even more likely because an 1801 birthdate would be four years before his parents' marriage.  Still, the later censuses should be checked.  Perhaps his parents' married date is incorrect.

4.  WorldConnect (online at RootsWeb.com).