Comprehensive Description

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(from Allan Hancock Pacific expeditions vol. 1 1943)

Genus TETRASTEMMA Ehrenberg
Nine species belonging to this genus have been found on the North Pacific coast. Only one of these is known to occur in other parts of the world.
--Key to Species--
1. With 4 well-developed ocelli....2
1. With 4 fragmented ocelli....aberrans

2. Dorsal surface with conspicuous brown stripes or rectangular markings or both....3
2. Dorsal surface without brown stripes or rectangular markings....6

3. Dorsal surface with 2, 4, or 6 brown stripes....4
3. Dorsal surface with brown rectangular markings and stripes....reticulatum

4. Flesh color, creamy, or grayish, with 2 brown longitudinal stripes on dorsal surface....T. bilineatum
4. Whitish, with 4 or 6 brown longitudinal stripes....5

5. With 4 brown stripes, of which 2 lie on dorsal surface and on lateral margins of body....quadrilineatum
5. With 6 brown stripes, of which 4 lie on dorsal surface and 2 on or slightly beneath lateral margins of body....sexlineatum

6. With large black or brown marking on dorsal side of head....7
6. Head without conspicuous marking....8

7. Cephalic marking wreathlike; reddish brown both above and below, except head which is white with a sharply marked dark brown or black wreath on dorsal surface....T. signifer
7. Cephalic marking triangular or shield shaped ; color highly variable except head, which is white with shield-shaped or triangular marking of dark brown color on dorsal surface; dorsal surface of body purple, brown with white dorsal longitudinal band, reddish with brown flecks, pale brownish or buff, sometimes with series of narrow transverse white markings ....T. nigrifrons


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© Ritger, Rebecca

Source: Nemertea

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