mammilla

The results indicated that the eggshell structures of four birds were much similar with other bird species , which were outer layer , spongy layer , cone layer , mammilla , shell membrane layer and pore channels through the shell from outer to inner .

结果显示，这四种鸟类的卵壳结构与其他鸟类的基本相似，由外而内依次为表层、海绵层、锥体层、乳突、壳膜层及贯穿卵壳的气孔道等。