THE ANNALS 
MAGAZINE OF NATURAL HISTORY. 
{FOURTH SERIES. } 
No. 87. MARCH 1875. 
XX.—On Pelagonemertes Rolleston. By H. N. Mosetey, 
Naturalist on board H.M.S§. ‘Challenger.’ 
[Plate XV. B.] 
Tuts remarkable form was found in the trawl, together with 
a number of deep-sea animals, from 1800 fathoms, near the 
southern verge of the South-Australian current, lat. 50° 1'S., 
long. 123° 4' E., March 7, 1874. Its appearance at once pro- 
nounced it a pelagic animal, the body beimg gelatinous and 
transparent, as in Salpa, with the exception of the alimentary 
canal, which stood out in relief, being of a deep burnt-sienna 
colour (as is the nucleus in many Salpe), and the region of the 
sheath of the proboscis, which was less transparent than the 
remainder of the body. The animal was living when obtained, 
and when placed in fresh sea-water gave evidence of life by a 
feeble irregular peristaltic contraction of the external muscular 
tunic, which increased on irritation; the proboscis was also 
protruded and retracted several times. 
The animal was about 4 centims. long and 2 broad, and 
5 millims. in thickness. Hence its dimensions, and especially 
its thickness, render it unfavourable for a perfect examination 
of its structure under the microscope whilst in the entire con- 
dition. As only one specimen was procured, and as this was 
believed to be unique, no dissection was resorted to, excepting 
the removal of a small portion of the epidermis and external 
muscular tunic for microscopic examination. Hence the 
investigation of the structure of this Nemertine necessarily 
Ann. & Mag. N. Hist. Ser. 4. Vol. xv. 12 
