How does the digestive system of Lingula differ from that of articulate lamp shells?

The digestive system of Lingula, an inarticulate brachiopod, differs from that of articulate lamp shells primarily in the presence of an anus.

In Lingula, the digestive system is a complete tract consisting of a mouth, gullet, stomach, intestine, and anus, all of which are surrounded by a digestive gland or liver.1

In contrast, articulate brachiopods possess a blind, U-shaped digestive canal that includes a mouth, a saclike stomach, and an intestine, but they lack an anus. Consequently, articulate brachiopods must excrete waste through the mouth. While both groups utilize a lophophore to filter food particles from the water, these fundamental differences in the structure of the digestive tract distinguish the two groups.12