viperidæ

from The Century Dictionary.

• The vipers; one of four families into which the suborder Viperina or Solenoglypha, of the order Ophidia, is divided, distinguished from the Crotalidæ by the absence of a pit between the eye and the nostrils, and from the Atractaspididæ, and Causidæ by the presence of a postfrontal bone in connection with ungrooved fangs.