44 
THE VOYAGE ^OE H.M.S. CHALLENGEK. 
Trochostoma antarcticum, n. sp. ,(P1. II. fig. 7). 
Habitat. — Station 306a, January 2, 1876 ; lat. 48° 27' S., long. '74° 30' W.'; deptfi, 
345 fathoms; bottom temperature, 46 ’0 ; blue mud ; a single individual. Station 307, 
January 4, 1876 ; lat. 49° 24' 30" S., long. 74° 23' 30" W.; depth, 140 fathoms ; bottom 
temperature, 46 '0 blue mud; one specimen. 
The specimen brought home from Station 306a has a length of about 40 mm. That 
dredged at Station 307 is much smaller. The only difference I have been able to observe 
between these forms and the species of von Marenzeller living in the Arctic Sea is found in 
the calcareous deposits, which are much more regularly constructed in the southern forms. 
From the scanty materials I must abstain, for the present, from offering any opinion on 
the validity of the new species proposed by me. 
The caudal portion of the body is comparatively short but very narrow, especially in 
the smaller individual. Some very minute papillae surround the anal aperture. The 
tentacles of the larger specimen have only three short processes, while those of the 
smaller individual seem to be furnished with about five. The tentacles being retracted, 
it is almost impossible to distinguish their true shape. 
According to Danielssen and Koren, the old individuals of Trochostoma arcticum 
have their tentacles provided with five to seven processes, while the young ones carry 
but three such processes on each tentacle. The integument is thin, transparent, colour- 
less, and very rough from numerous perforated calcareous tables consisting of a perforated 
disk and a straight outwardly directed long crown generally composed of three rods, 
which mostly carry spines and are connected with each other by several transverse 
beams. When fully developed, most of the disks of the tables have six larger holes and 
are of a more or less distinctly regular star-like form. Here and there a minute table 
may be found, composed of a triangular disk with three holes and a simple rod-like spire 
terminating in hooks (PI. II. fig. 7, d). In the posterior part of the body the deposits 
present a more irregular shape, and often have some smaller holes besides the larger ones. 
Diameter of the plates up to 0'2 mm. or more. Many different stages in the develop- 
ment of these deposits are to be seen within the integument. No other kind of deposits 
is present, 
Trochostoma albicans, n. sp. (PI. III. fig. 2; PI. XL fig. 3). 
Body elongated, anteriorly broadest, suddenly rounded and truncated, gradually 
tapering posteriorly into a very long slender, narrow, almost cylindrical caudal portion. 
Tentacles fifteen, short, with their terminal part rounded discoidal and surrounded by 
four or five short processes. Integument coriaceous or somewhat translucent, very 
rough, with only one kind of deposits, viz., numerous rather large and irregular perforated 
