1. horn core：除犀之外一般左右成对,牛、羊等的角是前额骨的突起,即角心(horn core)上覆以角鞘(horn sheath)称为洞角(hollowhorn). 长颈鹿是在短的角心上覆有皮肤. 鹿类只雄性有角,呈分枝状,称枝角,每年脱落更新. 初生时是以皮肤覆盖角心(袋角),
1. 它们额骨上生有一对不分叉的骨质角心，外被角质鞘，逐年增大而不脱落，只有角心附于头骨上保存为化石，角心的特征亦为牛类化石的重要鉴定依据。
They gave birth to a pair of frontal bone on bone does not fork mass angle heart, outside horny sheath, increasing year by year and not fall off, only angle Heart attached to the skull to save as a fossil, angular features of the heart is also an important identification of cattle based on fossils.
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2. 其实质是该磨钻头活动卡规是由主卡规和副卡规构成，卡心角与被卡钻头的锋角心位于同一条轴心上并在其卡规上设有指示刻度。
A clamping center angle and the sharp angle center of the clamped drill are positioned on the same shaft center, and the gauges are provided with indication graduations.