Encyclopaedia Britannica, 11th Edition, "Armour Plates" to "Arundel, Earls of"

bunodont ([Greek: bounos], a hillock) type of molar into one in which the four main tubercles, or columns, have assumed a crescentic form, whence this type is termed selenodont ([Greek: selaenae], the new moon). Further, there is the modification of the latter from a short-crowned, or brachyodont type, to one in which the columns are tall, constituting the hypsodont, or hypsiselenodont, type. It is noteworthy, however, that in some instances there appears to have been a retrograde modification from the selenodont towards the bunodont type, the hippopotamus being a case in point. Other modifications are the loss of the upper incisors; the development of the canines into projecting tusks; and the loss of the anterior premolars.