In both generations, the transverse ribs of the gill bar meet dorsally, narrowing sharply toward the ventral surface, so that they are far apart from one another ventrally. Solitary zooids: Test soft and smooth. Body elongate and cylindrical. Eight or 9 body muscles that extend rather far ventrally and are usually separated. MI to MIV converging, contiguous, or fused in the mid-dorsal line. A great variation is also found in the number of muscular fibers. Aggregate zooids: Body fusiform because of the presence of short anterior andposterior projections. Five body muscles, all of them meeting in the mid-dorsal region. Embryo between MIV and MV.