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Description

Travisia kerguelensis, n. sp. (Pl. XLIII. fig. 10 ; Pl. XXXVIA. figs. 1, 2).

 

Habitat.—Dredged at Station 149, in Betsy Cove, Kerguelen, at a depth of 25 fathoms, and apparently in peculiarly odoriferous mud, since the specimens still retain the scent. Nephthys and Brada were its companions in this habitat.

 

A large example measures about 20 mm. in length, with a diameter at its widest part of fully 7 mm.

 

The specimens have the usual dull whitish colour of the European Travisia forbesii, and appear minutely dotted under a lens from the glands. The number of segments is about the same as in the species just mentioned, viz., twenty-three, and in other respects the resemblance is close. In the Challenger form, however, the rings of the segments differ, and posteriorly the two last have a crenated margin dorsally, while the segment anterior to these also shows a few lateral pectinations. Moreover, the dorsal cirri are shorter, as are also the lateral caudal processes (Pl. XLIII. fig. 10).

 

The intestine is filled with dark sand, the coarse grains of which are covered over with numerous circular ova having a granular and probably adhesive investment for attaching them to the fragment, and tessellated here and there with smaller clear ovoid bodies ; while other sand-grains are hirsute with Diatoms. There is good reason, therefore, why this peculiar sand should be so utilised by the animals.

 

In section the characteristic condition of the cuticular tissues of the genus is strongly marked in this form. When viewed laterally the surface seems to be formed by a closely arranged series of papillæ (Pl. XXXVIA. fig. 1) with narrow pedicles, the whole resembling a series of closely arranged wine-glasses, for the narrow stem arises from an elevation of the tissues beneath. A careful examination, however, shows that the cuticle envelops each of these goblet-shaped papillæ, being thickest in the interseptal regions, and forming the main part of the stem, which is thus translucent. The stems merge into the cuticular coating of the inner region of the hypoderm, which is fibro­granular. The external part of the hypoderm (constituting the bowl of the wine-glass) is coarsely granular and opaque, and apparently represents the outer or glandular part of the hypoderm split up into many divisions by the envelopes of cuticle. When viewed from the surface (P1. XXXVIA. fig. 2) the skin is thus made up of a vast series of some­what hexagonal facets. The spaces around the stems of the goblets probably subserve the same functions as the smaller and more numerous areola) in the hypoderm of other forms. The circular fibres beneath the hypoderm are not much developed. The longitudinal muscular layers seem to be nearly continuous. The ventral longitudinal are separated only by a narrow pedicle, to which is attached the somewhat triangular nerve-area, the latter having a straight superior border of firm tissue (sheath), to the outer angles of which the oblique muscles are attached. The cords are rounded in transverse section. The central region of the body is occupied by voluminous folds of the alimentary canal. The nerve-area in this form thus slightly deviates from that in Travisia forbesii, which is situated between and somewhat above the oblique muscles, while other fibres are attached to the upper and outer curves of the region.

 

In the structure of the skin this form somewhat approaches Travisia glandulosa, procured at a depth of 1785 fathoms by the late Dr. Gwyn Jeffreys during the Arctic cruise in the "Valorous."1

 

(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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