Characteristics: The body musculature of the zooid is formed by complete transverse fibers anterior to the atrial siphon; porterior to it, there are short muscles fibers perpendiculars to the dorsal margin, only up to the middle of the body lenght. There are 13-18 rows of stigmata in branchial sac, 20-25 stigmata per row. Stomach wall smooth, without typhlosole nor internal ridges.