Аннотация:The plectolophous lophophore, which is an organ characteristic of the order Terebratulida, is themost complex lophophore type in recent brachiopods. In the present paper, we provide the first 3D reconstructionof the coelomic system of the plectolophous lophophore using an example of the terebratulid brachiopodCoptothyris grayi (Davidson, 1852). We have found that this coelomic system consists of three entirelyseparated compartments. The first compartment includes a periesophageal coelom, as well as paired smalland tentacle canals, and performs the transport and excretory functions. The second compartment consistsof a pair of large coelomic canals of the lophophore that act as its hydrostatic skeleton. The third compartmentis represented by a pair of brachial pouches connected with the perivisceral coelom that contain thediverticula of the digestive gland and allow the efficient use of the mantle cavity.