Planolites annularius Walcott, 1890

Diagnosis.—Horizontal, straight to curved, subcylindrical burrows with pronounced annulations (Pemberton & Frey, 1982; Fillion & Pickerill, 1990).

Description: Straight, smooth, unlined, unbranched, horizontal burrow, somewhat flattened, 23 mm in length and 1.5 mm wide, preserved in positive hyporelief on the sole of NBMG 10287 (see C. montanus for details). The burrow is characterized by regularly spaced, 0.3 mm wide, annulations oriented slightly obliquely to its long axis. Small size precludes determination of its fill, though this appears to be similar to the host rock.

Predominantly horizontal, straight to sinuous or undulose burrows exhibiting prominent annulations. Annuli may be of regular or irregular size and spacing; otherwise, burrows tend to be more or less constant in diameter. Most are stright to slightly curved, and are oriented parallel to subparallel to bedding. True branching has not been observed. Preserved primarily as hypichnal ridges and shallow endichnia; undulose specimens may exhibit both preservations.