KEPORT 01^ THE ANNELIDA. 
423 
“Gazelle.” Two common species are mentioned by Ehlers from the “Porcupine,” both 
from comparatively shallow water, and in the Norwegian North Atlantic expedition the 
greatest depth at which Cistenides liyperhorea was obtained was 263 fathoms. 
Petta, Malmgren. 
Petta assimilis, n. sp. (PI. XLVII. figs. 8, 9 ; PI. XXVIa. figs. 16-19). 
Habitat. — Trawled at Station 147 (between Prince Edward and Kerguelen Islands), 
December 30, 1873; lat. 46° 16' S., long. 48° 27' E.; depth, 1600 fathoms; bottom 
temperature 34°‘2, surface temperature 41°‘0; sea-bottom, Diatom ooze. 
A form devoid of its tube, measuring about 22 mm. in length, and with a diameter of 
4’5 mm. In this respect it is well to remember that the specimen is soft and flattened. 
It is a larger form than the British representative of the genus. The bright golden 
paleolse are also longer and more slender, their number being about fourteen on each side, 
while a few of the inner are very attenuate. The triangular membranous fold under the 
paleolae has an even margin. The anterior border of the first segment shows four or five 
well-marked fimbrise as in the British species ; and the following segment has more 
numerous though smaller appendages. Posteriorly the scapha has a different anal 
process from the species above mentioned, and the ligula is short and conical. The anal 
process forms a scale-like appendage to the scapha. 
There are seventeen pairs of bristles, which group themselves structurally into two 
series. The bristles of the first series (PI. XXVIa. fig. 16) possess stout shafts and 
tapering tips with a wing at each side merging toward the extremity into a double series 
of spikes by the splitting of the wings. These terminal serrations are much finer than 
in the British representative. The other series (PI. XXVIa. fig. 17) also have a wing at 
each side of the terminal region, but before much diminution takes place an enlargement or 
heel occurs, and then the bristle rapidly tapers to a fine point. The edge of the terminal 
region is finely serrated, and a space below the enlargement is in the same condition. 
The hook-like caudal bristles agree in arrangement with those in the British form, 
but they slightly differ in shape (PI. XXVIa. fig. 18), the tip being less tapered and less 
hooked. Certain wavy bands are also present in all, a short distance beneath the extremity. 
The hooks (PL XXVIa. fig. 19) very much resemble those of the British form (and 
also those of Malmgren’s Petta pusilla, if we add the minute serrations probably omitted 
by his artist on the third process), showing superiorly a smaller upper and a larger inferior 
fang, followed by a broad hook-like process (the third) bearing a series of minute denti- 
culations on its edge, and lastly a rounded base, less prominent than in the foregoing. 
The contents of the alimentary canal consist of a rich greyish- white mud, in which 
Glohigerince abound, but which likewise swarms with many beautiful Diatoms and fine 
