An exhaust gas treatment device of an internal combustion engine of a motor vehicle, wherein the exhaust gas treatment device partially purifies an exhaust gas flow from contaminants, wherein the exhaust gas flow is introduced through an inlet opening and then conducted through an outlet opening into an ambient atmosphere, and wherein the exhaust gas treatment device includes a housing that includes plural housing shells (4, 6), a) wherein at least one first housing shell of the housing shells (4, 6) is connected with at least one second housing shell by at least one disengageable connection (20, 22), b) Wherein the disengageable connection (20, 22) includes at least one centering ring (68, 70) through which the housing shells (4, 6) are in indirect contact with each other in at least one mounting plane (72, 74), c) wherein the at least one centering ring (68, 70) is a component that is separate from the housing shells (4, 6), d) wherein the at least one centering ring (68, 70) includes an inner centering collar, a center section that is arranged between ends (46, 48, 50, 52) of the housing shells (4, 6), and an outer centering collar, e) wherein the inner centering collar is configured to contact at an inner circumferential surface of the first housing shell and the outer centering collar is configured to contact at an outer circumferential surface of the second housing shell, or the inner centering collar is configured to contact at an inner circumferential surface of the second housing shell, and the outer centering collar is configured to contact at an outer circumferential surface of the first housing shell, f) wherein the outer centering collar includes a circumferential recess with respect to a circumference of the at least one centering ring (68, 70) so that the first housing shell and the second housing shell are movable relative to each other and disengageable from each other along the at least one mounting plane (72, 74) for assembly and disassembly, characterized in that g) the second housing shell has a U-shaped cross-section with a first arm and a second arm that are connected by a transversal branch, h) wherein the first housing shell is supported between the first arm and the second arm of the second housing shell respectively by a disengageable connection (20, 22), i) wherein a first end of the first housing shell indirectly contacts the first arm of the second housing shell through a first centering ring, and a second end of the first housing shell indirectly contacts the second arm of the second housing shell through a second centering ring, j) wherein at least one fold or bead is configured in a jacket wall in a portion of at least one end (46, 52) of a housing shell so that the jacket wall is elastically deformable in the portion. a) wherein at least one first housing shell of the housing shells (4, 6) is connected with at least one second housing shell by at least one disengageable connection (20, 22), b) Wherein the disengageable connection (20, 22) includes at least one centering ring (68, 70) through which the housing shells (4, 6) are in indirect contact with each other in at least one mounting plane (72, 74), c) wherein the at least one centering ring (68, 70) is a component that is separate from the housing shells (4, 6), d) wherein the at least one centering ring (68, 70) includes an inner centering collar, a center section that is arranged between ends (46, 48, 50, 52) of the housing shells (4, 6), and an outer centering collar, e) wherein the inner centering collar is configured to contact at an inner circumferential surface of the first housing shell and the outer centering collar is configured to contact at an outer circumferential surface of the second housing shell, or the inner centering collar is configured to contact at an inner circumferential surface of the second housing shell, and the outer centering collar is configured to contact at an outer circumferential surface of the first housing shell, f) wherein the outer centering collar includes a circumferential recess with respect to a circumference of the at least one centering ring (68, 70) so that the first housing shell and the second housing shell are movable relative to each other and disengageable from each other along the at least one mounting plane (72, 74) for assembly and disassembly, characterized in that g) the second housing shell has a U-shaped cross-section with a first arm and a second arm that are connected by a transversal branch, h) wherein the first housing shell is supported between the first arm and the second arm of the second housing shell respectively by a disengageable connection (20, 22), i) wherein a first end of the first housing shell indirectly contacts the first arm of the second housing shell through a first centering ring, and a second end of the first housing shell indirectly contacts the second arm of the second housing shell through a second centering ring, j) wherein at least one fold or bead is configured in a jacket wall in a portion of at least one end (46, 52) of a housing shell so that the jacket wall is elastically deformable in the portion.