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Comprehensive Description

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Description

Maldane sarsi, Malmgren.

 

Habitat.—Dredged at Station 232 (south of Yedo, Japan), May 12, 1875 ; lat. 35° 11' N., long. 139° 28' E. ; depth, 345 fathoms ; bottom temperature 41°·1, surface temperature 64°·2 ; sea-bottom, green mud.

 

The specimens are comparatively small when contrasted with the Canadian examples of the species. The only complete one measures about 48 mm., with a diameter of 1·5 mm. at its widest part.

 

The specimens agree in appearance, number of segments, and other particulars with the ordinary forms, the only point worthy of notice being the very distinct crenations of the ventral margin of the anal disk. The bristles and hooks coincide with those from Europe and America.

 

One specimen is in a friable tube composed of greyish mud. The outer layers could easily be removed, as usual, from the pale chitinous lining next the body of the animal.

 

The greyish mud in the alimentary canal abounds in Diatoms and Radiolarians, but with a very few minute sponge-spicules. Peculiar cylindrical transparent rods also are common, often with an acute point at one end, though sometimes with the point enclosed ; and when the apex is broken off a bifid condition is caused by the sloping sides of the cylinder remaining attached. A few fragments of minute Crustacea are also present.

 

In transverse section the body-wall differs from that of Praxilla and Nicomache in the much greater thickness of the cuticle and in the extreme attenuation of the circular coat, which, indeed, can hardly be discerned. The hypoderm is largely developed on the ventral and lateral walls of the body. The nerve-area, instead of being carried outward by the tense and thick circular coat as in the forms mentioned, passes inward between the longitudinal muscles. Moreover, no canal is present. This passage inward is probably connected with the rudimentary condition of the circular muscular coat. The longitudinal ventral muscles are massive internally but taper to a thin layer which goes upward almost to the dorsal arch. The oblique muscles thus arise from the superior lateral region, and are fixed to the circular coat on each side of the nerve-area. The longitudinal dorsal form a very thin sheet of fibres on each side of the median line. The fasciculi of the muscles are comparatively coarse. A corpuscular fluid occupies the perivisceral chamber.

 

The Clymene koreni of Hansen,1 from the Norwegian North Atlantic expedition, seems to belong to the same genus as the present form.

 

1Op. cit., p. 40.”

 

(McIntosh, 1885)

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Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© National Museum of Natural History, Smithsonian Institution

Source: Antarctic Invertebrates Website (NMNH)

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