Zygonemertes

(from Coe, W. R. (1901). Papers from the Harriman Alaska Expedition. XX. The nemerteans.. Proc. Wash. Acad. Sci.. 1-110.)

Montgomery (Zool. Jahrb., x, p.2 to 4, 12, 1897) has created a new genus for Amphiporus virescens Verrill based on its anatomical peculiarities, especially the structure of the proboscis and proboscis sheath. This genus he named Zygonemertes, with the following characters as its chief peculiarities:
(1) The proboscis sheath reaches to the end of the body, while (2) the thickened proboscis is but half as long; (3) basis of central stylet large, elongated; flattened or slightly concave posteriorly; (4) central stylet massive, not half the length of its basis: (5) ten or eleven proboscidial nerves; (6) body contractile, shape like Amphiporus, not as elongate as in Emplectonema; (7) ocelli numerous and small, extending along the nerve cords posterior to the brain.

While I am of the opinion that these characters are mainly of specific rather than of generic rank, yet I am convinced that because of the large number of species already in the genus Amphiporus the establishment of this new genus will be of great practical convenience. The most tangible characters of the group are: (1) the eyes extend posteriorly beyond the brain along the lateral nerve cords, and (2) the basis of the central stylet is massive and has a concave or a truncated posterior end, while the stylet itself is comparatively weak. Of course the number of nerves in the proboscis cannot be considered a generic character. There are two Alaska species, then, which may be placed in the genus--Z. thalassina, which is closely allied to the type species, and Z. albida, which is a minute, white form.

(from Coe, W. R. (1905). Nemerteans of the west and northwest coasts of America. Bull. Mus. comp. Zool. Harv.. 1-318)

Body is long and slender, but not so elongated as in Emplectonema; head broader than neck in life, provided with two pairs of lateral oblique furrows; ocelli small and very numerous, extending posteriorly far beyond brain and above the lateral nerve cords: proboscis sheath extends to posterior end of body, while proboscis is comparatively short; armature of proboscis much as in Amphiporus although basis of central stylet is massive and has a concave or truncated posterior end, while stylet itself is comparatively weak; usually 10, 11, or 12 probascidial nerves.
The worms are peculiar in life because of their long, contractile bodies and broad heads, and are especially remarkable because of their extremely active habits, being very restless in confinement and in almost constant motion, often crawling out of the water and lip the sides of the vessel in which they are contained.

(from Allan Hancock Pacific expeditions vol. 1 1943)

Genus ZYGONEMERTES Montgomery

Three closely similar and possibly intergrading species of this genus have been found on the Pacific coast.

Key to Species

1. Central stylet very short and stubby ; basis about 3 times as long as stylet, with serrated posterior edge; 4-5 accessory stylets in each pouch; 12 proboscidial nerves....thalassina
1. Central stylet moderately slender; basis about twice as long as stylet, without sharply serrated posterior edge; 2-3 accessory stylets in each pouch; 10 or 11 proboscidial nerves....2

2. Color white or pale yellow....albida
2. Color whitish when young, becoming pale yellow, pink, orange, brown, red, or green when mature....virescens

Zygonemertes is a genus of worms belonging to the family Zygonemertidae.

The species of this genus are found in North America.

Species:

Zygonemertes africana Stiasny-Wijnhoff, 1916 Zygonemertes albida Coe, 1901 Zygonemertes algensis (Bürger, 1895) Zygonemertes capensis Wheeler, 1934 Zygonemertes cocacola Corrêa, 1961 Zygonemertes fragariae Corrêa, 1954 Zygonemertes glandulosa Yamaoka, 1940 Zygonemertes isabellae Corrêa, 1954 Zygonemertes jamsteci Kajihara, 2002 Zygonemertes luederitzi Stiasny-Wijnhoff, 1916 Zygonemertes maslovskyi (Czerniavski, 1880) Zygonemertes shintai Kajihara, 2002 Zygonemertes simoneae Corrêa, 1961 Zygonemertes tenuirostris Korotkevich, 1977 Zygonemertes thalassina Coe, 1901 Zygonemertes virescens (Verrill, 1879) Zygonemertes wadjemupensis Gibson, 1999 Zygonemertes zhenylebedevi Chernyshev, 1991