Wiktionary
protocone
n. (context anatomy English) A cusp in the corner of an upper molar tooth in mammals
Wikipedia
Protocone
thumb|500px|right|Right upper molar showing the four main upper molars cusps.
The protocone is a cusp of the molars of the upper dentition in Placental and Marsupial vertebrates. It is found at the mesiolingual area of the tooth. The crests between the cusps are adaptations for slicing food during occlusion or mastication (chewing).
Other cusps of the upper dentition of hominids include the paracone, hypocone, and the metacone.