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Description

Oridia limbata (Ehlers).

 

Oria limbata Ehlers, 1897, p. 137, pl. IX, figs. 211-216, and 1913, p. 579 ; Oria limbata Fauvel, 1916, p. 476.

 

Rioja (1923, p. 52) states that the name Oria is preoccupied for a genus of insects, and he suggested in 1917 that de Quatrefages' generic name must be replaced now by the above. It appears that Chamberlin in 1919, unaware of Rioja's emendation, proposed the name Oriades for the same reason.

 

A number of these small free-living Sabellids were obtained off Cape Adere ; some of them had been preserved in osmic acid, others in alcohol. They are rather longer than the type, the total length being 5 mm.

 

I find that the gill filaments carry ten pairs of barbules, all of which reach up to, or even extend beyond, the tip of the filament.

 

I do not detect the ovate ciliated processes inside the gill-base which are de­scribed by Ehlers, owing perhaps to the way in which the mounted specimens are lying, but I see the two larger processes at the base of the dorsally situated filaments.

 

The characteristic membrane along the gill filaments is even better developed here than it appears to be from Ehlers' figure 214 ; I find it broader and longer than he shows ; it has in my specimens a well-defined edge and in spite of its tenuity the membrane is rendered very evident by the attachment to its surface of a number of Protozoa, apparently some form of Vorticellid.

 

In the collar of the type a triangular lobe is represented as projecting forwards on the ventral region; this I do not detect in cleared specimens, where the collar appears to be of uniform height right across this region.

 

Like Fauvel, I am unable to detect either the otocysts in the 1st segment or the eyes at either end of the worm ; and Ehlers himself (1908) states that the former are difficult to see in preserved specimens. I treated one individual with potash and mounted it in glycerine. Failing to see the above organs, I stained and mounted the worm in Canada balsam in order to make it more transparent ; but was unsuccessful even then. But in spite of these slight discrepancies I have no doubt it is the same species as that described by Ehlers.

 

Locality.—Off Cape Adere, Station 220, depth 45-50 fathoms. Distribution.—Tierra del Fuego ; Kerguelen ; Kaiser Wilhelm II Land (Ehlers) ; Falkland Is. (Fauvel).”

 

(Benham, 1927)

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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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