408 
THE VOYAGE OE H.M.S. CHALLENGER. 
Praxilla gracilis and Praxilla arctica. The crown is not much elevated in profile, 
though six or seven teeth are noticeable above the great fang. The fibres arise close 
under the base of the latter. 
The soft sandy mud in the alimentary canal contains Glohigerince and other 
Foraminifera, the long cylindrical siliceous structures, each with a pointed extremity, a 
few small Diatoms, and occasionally a fragment of a sponge-spicule. 
The condition of the specimen is unsatisfactory for minute description, and the 
cuticle and hypoderm have disappeared. The circular muscular coat is of remarkable 
thickness, but the longitudinal shows no feature of note. Two greatly dilated vessels 
occur in the dorsal median line over the alimentary canal, and a considerable ventral 
trunk lies over the nerve -area. 
Praxilla (?) fragment (PI. XXIXa. fig. 15). 
Habitat. — Dredged at Station 76 (off the Azores), July 3, 1873 ; lat. 38° 11' N., 
long. 27° 9' W. ; depth, 900 fathoms ; bottom temperature 40°'0, surface tempera- 
ture 70°’0 ; sea-bottom, Pteropod ooze. 
A fragment, apparently of a small Praxilla, the hooks of which (PI. XXIXa. fig. 15) 
present about five teeth above the great fang. The shoulder is well marked, and a 
distinct interval occurs between the great fang and the vibrissse. 
The tube, which is in fragments, is almost entirely composed of Glohigerince, large 
and small, with sand-graius and a few sponge-spicules. The surface of the tube, with 
its coarse Glohigerince, affords a contrast to the finer mud swallowed by the minute 
inhabitant. 
Praxilla ahyssorum, n. sp. (PI. XLVI. figs. 10, 11 ; PI. XXXVII. fig. 5 ; 
PI. XXXIXa. figs. 1,10). 
Habitat. — Trawled with Maldanella antarctica at Station 157 (in the Antarctic 
Ocean), March 3, 1874; lat. 53° 55' S., long. 108° 35' E. ; depth, 1950 fathoms; sea- 
bottom, Diatom ooze. 
The specimen is incomplete, but measures about 58 mm. in length, and barely 
2 mm. at its widest diameter in front. 
■ There are nineteen segments of the body in the fragment. The truncated snout 
has a little obliquity, but not much, and a slightly raised thickened margin all round, 
with a deep notch at each side, while the anterior border is the more elevated. The 
face, or cephalic plate, is marked by the usual median elevation (PI. XLVI. fig. 11) and 
flat, hoof-shaped lateral depressions. There is nothing special in the appearance of the 
