The Collaborative International Dictionary of English v.0.48:

Periwinkle \Per"i*win`kle\, n. [OE. pervenke, AS. pervince, fr.
   L. pervinca.] (Bot.)
   A trailing herb of the genus Vinca.
   [1913 Webster]

   Note: The common perwinkle (Vinca minor) has opposite
         evergreen leaves and solitary blue or white flowers in
         their axils. In America it is often miscalled myrtle.
         See under Myrtle.
         [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Myrtle \Myr"tle\ (m[~e]r"t'l), n. [F. myrtil bilberry, prop., a
   little myrtle, from myrte myrtle, L. myrtus, murtus, Gr.
   my`rtos; cf. Per. m[=u]rd.] (Bot.)
   A species of the genus Myrtus, especially Myrtus
   communis. The common myrtle has a shrubby, upright stem,
   eight or ten feet high. Its branches form a close, full head,
   thickly covered with ovate or lanceolate evergreen leaves. It
   has solitary axillary white or rosy flowers, followed by
   black several-seeded berries. The ancients considered it
   sacred to Venus. The flowers, leaves, and berries are used
   variously in perfumery and as a condiment, and the
   beautifully mottled wood is used in turning.
   [1913 Webster]

   Note: The name is also popularly but wrongly applied in
         America to two creeping plants, the blue-flowered
         periwinkle and the yellow-flowered moneywort. In the
         West Indies several myrtaceous shrubs are called
         myrtle.
         [1913 Webster]

   Bog myrtle, the sweet gale.

   Crape myrtle. See under Crape.

   Myrtle warbler (Zool.), a North American wood warbler
      (Dendroica coronata); -- called also myrtle bird,
      yellow-rumped warbler, and yellow-crowned warbler.

   Myrtle wax. (Bot.) See Bayberry tallow, under Bayberry.


   Sand myrtle, a low, branching evergreen shrub (Leiophyllum
      buxifolium), growing in New Jersey and southward.

   Wax myrtle (Myrica cerifera). See Bayberry.
      [1913 Webster]

Easton's 1897 Bible Dictionary:

Myrtle
(Isa. 41:19; Neh. 8:15; Zech. 1:8), Hebrew hadas, known in the
East by the name _as_, the Myrtus communis of the botanist.
"Although no myrtles are now found on the mount (of Olives),
excepting in the gardens, yet they still exist in many of the
glens about Jerusalem, where we have often seen its dark shining
leaves and white flowers. There are many near Bethlehem and
about Hebron, especially near Dewir Dan, the ancient Debir. It
also sheds its fragrance on the sides of Carmel and of Tabor,
and fringes the clefts of the Leontes in its course through
Galilee. We meet with it all through Central Palestine"
(Tristram).

U.S. Gazetteer (1990):

Myrtle, MN (city, FIPS 44890)
  Location: 43.56318 N, 93.16288 W
  Population (1990): 72 (36 housing units)
  Area: 0.3 sq km (land), 0.0 sq km (water)
Myrtle, MO
  Zip code(s): 65778
Myrtle, MS (town, FIPS 50280)
  Location: 34.55928 N, 89.11581 W
  Population (1990): 358 (159 housing units)
  Area: 1.5 sq km (land), 0.0 sq km (water)
  Zip code(s): 38650
Myrtle, WV
  Zip code(s): 25670