Basinet or Bacinet
[bas-uh-nit, -net, bas-uh-net]
Etymology: Middle English bacinet, from Anglo-French, diminutive of bacin

Relatively light helmet with a rounded or pointed top. It might be fitted with a visor.
  (Prestwich, Michael. Armies and Warfare in the Middle Ages: The English Experience, 347)

*term definition retrieved from Netserf’s Medieval Glossary (http://www.netserf.org/Glossary)