48 THE VOYAGE OF H.M.S. CHALLENGER, 



very small ones posteriorly at its base. Integument very thin, transparent, with three 

 sorts of calcareous deposits numerous : large and small, spinose, three-armed bodies ; 

 unbranched or irregularly branched, spinose spicula ; and small spicula, curved in the 

 form of a C. 



Colour in alcohol, light violet. Breadth about 15 to 17 mm. 



HaUtat.— Station 158. March 7, 1874. Lat. 50° l' S., long. 123° 4' E. Depth, 

 1800 fathoms ; bottom temperature, 0"3 C. ; globigerina ooze. One incomplete specimen. 



As the posterior part of the body is torn off in this very interesting and character- 

 istic species, it is quite impossible to determine the length of the body, the position of 

 the anus, or the number of the pedicels. The remaining part of the body measures 

 about 35 mm. in length. Anteriorly, where the large dorsal appendage arises, the 

 body reaches its greatest height, and from that point the dorsal surface is almost 

 vertically bent down towards the tentacles. The dorsal surface is extremely convex, 

 the ventral, on the contrary, is almost flat or slightly convex, the breadth of the body 

 seems to be almost equal throughout, The circular ends of the tentacles are large and 

 sole-like. Only six pairs of pedicels remain, the first one arising close to the tentacles ; 

 their form is conical, strongly tapering towards the ends, which present a small sole-like 

 enlargement. The dorsal appendage is of considerable size, measuring about 25 to 

 30 mm. in length, broad superiorly, and almost flat ; its inferior part, on the con- 

 trary, is a little narrower, and has the posterior surface grooved in the form of a 

 gutter. Of the four projections in the upper free margin of the lobe the two in the 

 middle are largest. The whole lobe of this specimen is constituted, like that of the 

 preceding species provided with such appendages, by four long processes which, com- 

 municating with the dorsal ambulacra, are webbed together by an extension of the 

 integument, leaving only their tops free. The integument is very transparent, and the 

 strongly pigmented ambulacra, as well as the nerve-cords and the ambulacral cavi- 

 ties are plainly visible through it. The form and the size of the calcareous deposits 

 (PI. XXXIII. fig. 15) vary greatly. The large three-armed bodies are more scattered 

 in the integument, and have their arms straight, spinose, and measuring about - 22 mm. 

 The small three-armed deposits, on the contrary, are very crowded, and their arms, 

 measuring only about 0'06 mm. in length, are provided with conspicuously large spines; 

 the difference between these two deposits is thus striking. The arms are generally 

 straight and, arising from a common centre, form with each other angles of almost 

 equal size ; but it is necessary to add that many exceptions are found, some arms 

 being more or less irregularly curved, and consequently the angles being of unequal 

 size. The spicula unbranched, or sometimes which are provided with one or several 

 branches, are very scattered and strongly spinose. The small C-shaped spicula, 

 attaining a length of about 0"068 mm., present an enlargement in the middle, the 

 existence of which seems to be common to all deposits of this kind. Their 



