Furrows and ridges on the surface were caused by deforming ice. Farmers plant after the first rains in fields consisting of alternating ridges and furrows. The arched mouth lacks conspicuous furrows or enlarged pores at the corners. Birds have been recorded foraging for insects in furrows in freshly ploughed fields. This system switched the positions of furrows and ridges between growing seasons. Endoscopically, ridges, furrows, or rings may be seen in the esophageal wall. The corners of the mouth are devoid of furrows or folds. For example, not everyone furrows their brow when they are feeling angry. These pollens have three or more pores set in furrows called colpi. They also present upper and lower labial furrows. The occlusal surface of the molars is generally smooth but with longitudinal furrows. Spreading away from the furrows are smaller grooves called "feathering" or "cracking". Around twenty horizontal, parallel furrows cross on these bands. The mouth is small and curved, with prominent furrows at the corners. The pollen is about in length with three furrows which have one pore each.