Comprehensive DescriptionRead full entry
(from Coe, W. R. (1901). Papers from the Harriman Alaska Expedition. XX. The nemerteans.. Proc. Wash. Acad. Sci.. 1-110.)
Head with deep, horizontal furrows. Proboscis usually with three muscular layers and muscular crossings. Caudal cirrus present. Body rather firm; incapable of swimming.
(from Coe, W. R. (1905). Nemerteans of the west and northwest coasts of America.. Bull. Mus. comp. Zool. Harv.. 1-318)
This genus includes mostly moderately small, slender forms, generally less rounded posteriorly, and of rather more active habits than Lineus. Its most marked distinction from the latter genus is that the posterior extremity of the body is provided with a slender, usually colorless, muscular caudal cirrus. This is formed of a continuation of the muscular tissues and integument beyond the posterior end of the alimentary canal.
The proboscis is usually slender and comparatively weak; the proboscis sheath is sometimes considerably shorter than the body.
The species of Micrura are generally, though not always, more brightly colored and have more distinct markings than do those of Lineus. The vast majority of the species arc provided with numerous ocelli, though some are blind.
The head is slender, and not distinctly separated from the rest of the body. The lateral faces of the body are not provided with thin edges as in Cerebratulus, the intestinal region is not so much flattened, neurochord cells are present in comparatively few species, and none of the species are able to swim as do all species of Cerebratulus. The mouth is usually smaller than in Cerebratulus, and the intestinal lobes are not so deep.