Bostrichobranchus pilularis (Verrill, 1871)
Bostrichobranchus pilularis is a solitary tunicate, which occurs unattached in soft sediments. Its globular shaped body is covered with a thin layer of mud, and, when its siphons are retracted, it looks like a small soft ball of mud. The tunic of the body, when cleaned, is very thin, soft, nearly transparent, thickly covered with minute granules, and composed of minute fibers, usually concealed by the adhering particles of mud and fine sand. The siphons are naked, nearly transparent, slender, tapered, and as long as the diameter of the body. They originate close together and are slightly divergent, with both of them being nearly straight. The siphons are completely retractable, and their bases are surrounded and connected by a narrow, naked, oval or oblong band, which is usually conspicuous when the tubes are contracted. The oral siphon is a little shorter than the atrial, the aperture surrounded by six acute, conical papillae, and twelve small dark brownish spots. The atrial siphon has a small square aperture, surrounded by four small lobes and four small, reddish brown eyespots. In life, when cleaned, the body is transparent and grayish, with the dark intestine showing through very distinctly, and the siphons with greenish coloring at their base. The diameter is usually about 5 mm, and seldom more than 6-8 mm (Verrill 1871; Van Name 1945).