Comprehensive DescriptionRead full entry
(from Coe, W. R. (1901). Papers from the Harriman Alaska Expedition. XX. The nemerteans.. Proc. Wash. Acad. Sci.. 1-110.)
Body of large size, rather stout, usually much rounded in the esophageal region but flattened posteriorly. Head not marked off from body, of variable form, in some states of contraction often emarginate in front. There is commonly a pair of inconspicuous oblique furrows back of head. The nerve cords and blood vessels join on the dorsal side of the posterior end of the intestine.
The mouth opens into the rhynchodaeum. The proboscis sheath commonly reaches but little beyond the middle of the body--in P. peregrine to 3/4 the distance towards the posterior extremity. The proboscis is small (P. pallida), of medium size (P. peregrina), or large (P. carnea). There is a single central stylet in the proboscis, and usually four or more pouches of accessory stylets. Some individuals of P. peregrina, however, have but two. Ocelli are numerous and minute. The cerebral sense organs are rather small and lie in front of the brain. Submuscular glands are usually well developed.
The species of this new genus show considerable resemblance to those of Emplectonema Stimpson. They differ, however, in general shape and appearance of body, never being very long or slender, and individuals do not coil their bodies into a mass as those of Emplectonema are so prone to do. The proboscis is much larger and the central stylet is always well developed. The proboscis sheath is also much longer. In many respects the genus resembles Amphiporus. The body is much longer, however, and not nearly so contractile, the proboscis is not nearly so large, and the proboscis sheath is not so long.